Two cultivars of tobacco with contrasting sensitivity to ozone have similar photosynthesis at low light intensity, but at high light, photosynthesis of the sensitive cultivar Bel-W3 was lower than that of the resistant cultivar Havana. In contrast, the electron transport rate at photosynthesis saturated light intensity was higher in Bel-W3 than in Havana. This excess may require efficient mechanisms to dissipate energy and oxygen radicals. We found that the non-radiative dissipation was lower in Bel-W3 than in Havana and that the conversion between violaxanthin and antheraxanthin + zeaxanthin was not complete in the ozone sensitive cultivar. Violaxanthin may have been partly converted in ABA. The high content of ABA may have caused stomatal closure and explain why photosynthesis at high light was reduced in Bel-W3 in comparison to Havana. β-Carotene content was also lower in Bel-W3 than in Havana. A low β-carotene content coupled with an inefficient use of the xanthophyll mechanism may contribute to determine the ozone sensitivity of Bel-W3 leaves.