The number of north Americans who went to the cinema in 2010 was around 5% down on the 2009 total, figures show.
Box office analysts at Hollywood.com forecast 1.35 billion tickets will be sold by the end of the year, down on the 1.42 billion sold in 2009.
It is the biggest year-on-year drop since 2005, making 2010 the second-lowest attended year of the decade.
Yet box office revenues remained about the same at $10.6bn (£6.9bn), due to increased ticket prices.
Animated movie Toy Story 3 was the highest-grossing film of the year at the US box office, earning nearly $415m (£267m).
The Pixar sequel, like second highest-grossing title Alice in Wonderland, was one of several hit movies released in 3D.
The higher ticket prices such titles afford were one of the reasons overall takings remained steady, according to Paul Dergarabedian of Hollywood.com.
"Without that we'd be looking at revenues that may not even have surpassed $10bn (£6.5bn)," he said.
Comic book sequel Iron Man 2, the third highest-grossing film of 2010 in North America, was the highest grossing movie not shown in the stereoscopic format.
It is thought attendance figures in the US and Canada will rise next year, when sequels to hit comedy The Hangover and Pirates of the Caribbean are released.