Rafael Lozano-Hemmer, a Mexico-born, Canada-based electronic artist, has an installation at the Barbican Art Gallery until January 18, and another in Trafalgar Square from November 14 to 23. Three of his new interactive works open at Haunch of Venison, London, on Wednesday.

My home in Montreal resembles a set from a 1970s porn movie. Open plan, low ceilings, brown-painted walls, different levels, swimming pool. Not that what goes on in here is steamy these days. I'm a family man with three kids.

I find the idea of collecting objects problematic; vampiric. The obsessive filling of gaps; the desire for things to be preserved. So I collect insubstantial things like superstitions. My favourite is the Spanish practice of throwing your underwear out of the window at New Year, just before the chimes. I've also assembled a collection of embarrassing dance moves, top one being the "contemptuous back kick". I also collect artists' manifestos - starting with the Futurist Manifesto of 1909 and finishing with my own OK ART manifesto. Not the actual manifestos, of course, but their contents. They're bombastic, totalitarian, politically incorrect. I love the way they crystallise an artist's passions.

The actual, physical art I own is by my friends. In the dining room I have wonderful, phantasmagoric photographs of hands by the Spanish photographer Daniel Canogar, covering an entire wall almost like wallpaper. My living room is dominated by a beautiful steel sculpture, "Explosición", by the Mexican artist César Martínez Silva. In order to generate the beautiful, anthropomorphic, violent shapes on its surface, he painted the steel with dynamite before burying it in the ground and detonating it. In my bathroom I have a photograph of a disgusting bathroom in Moscow taken by a friend in 1981. Thankfully my real bathroom is very clean. I also have lots of my own work around the place. "33 Questions per Minute" is a sculpture in which liquid crystal displays are programmed to ask 55bn different questions, just fast enough for you to read a given question, but not long enough for you to answer. Here's one: "Will you bleed in an orderly fashion?"

If the house was on fire, I'd grab my painting by the British-born surrealist Leonora Carrington, given to me by my mom. It shows an outrageous, sexy woman, sitting before a galaxy background. When I get round to hanging her, I'll put her in the bedroom, where she belongs.

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Richard Day, Old Master drawings dealer, 14 Old Bond Street, London, is publishing his memoirs 'Artful Tales' (£30).

When I joined Sotheby's 50 years ago, the chairman Peter Wilson told me: "I don't want anyone to be an expert if he doesn't collect himself." So I started collecting, which was quite a challenge as my pay was £8 a week. Furthermore, in order to be presentable at the various social occasions which came with the job, that money had to extend to a morning coat, white tie and tails, dinner jacket and two suits.

Most of my early purchases were Victorian pictures: a pretty portrait of a mother and child by the English painter George Chinnery (1774-1852) cost me £4. I also bought a very early David Hockney. I never paid more than £25. During this period I also started wearing - and collecting - bow ties. I've got between 50 and 60. Every time I buy one I feel a twinge of guilty pleasure.

My wife and I live in a small village in north-west Essex, close to where Eric Ravilious and Edward Bawden had their artists' colony nearly a century ago. It's picture-postcard perfect; opposite are the Norman church and the cricket pitch. Inside we've painted the walls buttermilk, with Old Master drawings on the walls and a Scottish grandfather clock ticking in the corner.

Any new acquisitions tend to be produced by me. I paint "portraits" of people's houses, often as thank you presents after having been to stay. I've done them for the Corsini family in Florence, and for Paul Mellon, of his house in Antigua. The most recent was an aerial view of Lord Carrington's house which Christie's employees presented to him when he retired as chairman. They'repainted in gouache and watercolour. I've hung photos of them along the hall.

The object I least like is a fake Fragonard slipped into the market by one of the knaves featured in Artful Tales. I keep it hidden underneath a cupboard in my dressing room because I don't know what the hell to do with it. Strictly it belongs to the father of a client, only he died. I can't destroy it because it doesn't belong to me. And, anyway, I think it has a right to exist.

My favourite is an embroidery on black silk by Mrs Delany. She was this amazing 18th-century lady who produced extraordinary floral collages, silhouettes and needlework. Ninety per cent of her work is now in the British Museum. I was at a sale in Norfolk when I stumbled upon it. "That's Mrs Delany," I thought. It cost me £150.

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Anita Zabludowicz, contemporary art collector and founder of 176, a contemporary art project space in Kentish Town, London

When I first became interested in collecting, back in 1994, I thought I wanted a Bacon, a Freud, a Nicholson, a Hepworth - one representative work by each of the modern British greats. My husband and I got as far as buying a Nicholson and an Auerbach before he discovered the contemporary American artist Matthew Barney. That was it. We were addicts. There's something amazing about the work of living artists. You enjoy "the now" through their eyes. A good example of this is the four Jake and Dinos Chapman portraits of my children in our hallway. One's a monster, another's a fly, the third's a gawky little thing and the fourth's a fairy.

One of my favourites is a painting by a Chinese artist called Ling Jian, showing a beautiful girl with Chairman Mao's Red Book bound to her back. I also love my drawing by the Irish artist David Haines of adolescent boys, complete with real chewing gum stuck to their faces.

My children pick the art in their rooms. Roy, 18, likes young artists and hangs their work alongside his collection of Russian and Chinese communist-era posters. Liam, 12, collects globes. In the main they're snow scenes but I've boosted his collection with a few "disaster globes" by an artist called Sherri Hay, containing buildings with people falling out or cars clinging to cliffs.

Every autumn I completely rehang the place. This time I'm going political, with works by Wolfgang Tilmans and Mary Kelly. I hate storing things away. It's not nice to the artists, so I do my best to find somewhere for them, either in 176 or in the barn of our house in Finland. The more I collect the bigger my conscience gets! A few things never leave the house, though: "Quantum Cloud XXXII" by Antony Gormley, as well as my Ben Nicholson painting, "Box and Cox", the first thing I ever bought.

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Lars Tharp, an expert on ceramics for the BBC's 'Antiques Road Show', is the newly appointed director of the Foundling Museum, London

I don't collect, which might seem strange to some people. Blame the chocolate factory syndrome: the more you handle beautiful things, the more your appetite for ownership is satisfied. Not to mention the more selective your taste becomes!

Furthermore, as a Scandinavian, born in Copenhagen, I believe that less is more. If I were rich I'd love to own one of those austere interior scenes by my countryman Vilhelm Hammershøi (1864-1916). I've had a shot at creating a Hammershøi ambience at home in Leicester, by painting the walls grey and acquiring a classic Danish sofa. On occasion my wife obliges me by standing with her back to me, and, behold, a Hammershøi tableau.

Having said that, I do buy things from time to time. Anyone walking into our house would notice my interest in Chinese ceramics, albeit most of what we have is broken, chipped or cracked. The modern English pottery is in better nick. Take this white vase by the Yorkshire potter Penelope Withers. It's tall and teetering off-centre; I love the way it shows how wayward clay can be, and how, over thousands of years, man has struggled, and triumphed, over giving it form.

But the first thing you see on entering our house is an 18th-century edition of "The Harlot's Progress", a six-part print sequence by William Hogarth. Ironically it's ceramics I have to thank for my obsession with Hogarth. In 1982 I was wandering through the National Gallery and paused beside Hogarth's series of paintings, "Marriage à la Mode". What struck me was not so much the titillating tale of cuckoldry as the quantities of ceramics featured - either as neutral furnishings or as satirical symbols poking fun at the "contagion of china fancy", as Samuel Johnson put it, which gripped society in 18th-century England.

Since then, my passion for Hogarth has snowballed. In fact, it's almost overtaken ceramics. My new charge, the Foundling Museum, owns no fewer than three masterpieces by Hogarth. As its new director I look forward to "owning" them vicariously.