The Australian international is particularly potent in the air, something which may encourage Everton given Arsenal's recent problems in dealing with Birmingham's Nikola Zigic and Newcastle's Andy Carroll.
But Wenger, who guided his side to a 6-1 win at Goodison last season, says Cahill is a different type of threat.
"Zigic and Carroll are dominating the air because of their size and their physical power," said Wenger.
"Cahill is more about timing and his accuracy in heading. When he heads the ball the 'keeper always has to make a save.
"I'm impressed by the way he wins some challenges against big centre halves," added the Arsenal boss.