THE works of the American artist Mark Rothko may be admired throughout the world and sell for tens of millions of pounds, but even experts have a problem with them — nobody can decide which way round they should hang.

Curators of the blockbuster Rothko exhibition at Tate Modern in London have displayed two of the artist’s best known works on their side, contrary to Rothko’s original intentions.

The two paintings from the Black on Maroon series have been hung vertically with bold stripes running from top to bottom. However, Rothko said he wanted the works — which he donated to the Tate before committing suicide in February 1970 — to be hung with the stripes running horizontally. His signature on the back of the paintings is thought to reflect this wish.

Rothko outlined his request in a series of discussions with Norman Reid, then director of the Tate, before the paintings first went on display in 1970. Archives reveal that Reid even sent Rothko a model of the gallery room for his approval.

Yesterday visitors to Tate Modern were surprised to learn that the paintings may have been displayed incorrectly.

“It definitely makes a difference,” said Laura Wilkinson, 28, who works in marketing. “It changes your interpretation. If that’s the way Rothko wanted it, that’s the way it should be hung. You wouldn’t hang a landscape upside down.”

Brent Webster, 44, a hotel worker, disagreed. “I prefer them vertically in this context,” he said. “That’s the beauty of abstract art; you have that freedom of interpretation.”

The Tate has agonised for decades over how the Black on Maroon paintings, which were created in 1958 and 1959, should be hung.

Although Reid followed Rothko’s instructions in 1970, he changed his mind nine years later after taking advice from a colleague and displayed the two paintings with the stripes running vertically.

In 1987, the works were returned to their horizontal hang for a special Rothko exhibition. The catalogue at the time stated that the artist’s signature on the back of the canvasses indicated that this was the correct position.

However, when the paintings were moved to the Rothko Room at the Tate Modern in 2000, they were once again shown on a vertical axis.

Achim Borchardt-Hume, the curator of the latest retrospective — which brings together Rothko paintings from around the world, including some of his black abstracts — partly stuck to the vertical hang so the Black on Maroon paintings match the height of other murals on display.

Some of the confusion, which is revealed in The Art Newspaper, may stem from Rothko himself. A deed of gift he signed in 1969 lists the two disputed paintings as vertical portraits.

“Rothko was always prevaricating over how his art should be shown,” said Waldemar Januszczak, art critic for The Sunday Times. “To me, the hang of these two paintings in the current exhibition seems right. But if it is clear that Rothko himself wanted them to be horizontal, you would be crazy to go against his wishes.”

Tim Marlow, an art historian, said: “I’m sure Rothko was wrestling with these big spatial concerns, so there is an ambiguity. Because of this, the Tate has a certain latitude.”

Rothko is not the first artist who may have suffered the ignominy of having his work displayed the wrong way up.

A painting by Vincent van Gogh called Long Grass with Butterflies briefly hung upside down in the National Gallery in 1965 before the mistake was spotted by a schoolgirl.

Some art critics claimed Four Fishermen’s Wives of Cadaques by Salvador Dali was displayed upside down in 1994 at the Hayward gallery on London’s South Bank. Although the painting’s blue sky and blue sea appear indistinguishable, curators insisted they were correct.

“Now nearly always an artist will indicate by signature or an arrow which way a picture should hang,” said Matthew Flowers, who owns galleries in Mayfair and Shoreditch.

This weekend Tate Modern said it would not be able to check Rothko’s signature on the two paintings until its exhibition ends in February. The gallery said: “We believe it’s more appropriate for these two paintings to be hung vertically.”

Additional reporting: Georgia Warren

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010