This study examined gender differences in students' scientific literacy as measured by OECD-PISA. In particular, we focused on the 2437 students from 140 Hong Kong schools. Hong Kong boys' and girls' science scores did not differ overall. However, boys scored higher than girls at the higher percentiles (75th and above). Moreover, specific test components showed gender differences. Boys tended to score higher on tests with more earth and physical science items, understanding of scientific knowledge items, and closed items. Meanwhile, girls tended to score higher on "recognizing questions" and "identifying evidence" items. These results suggest that a science test assessing diverse content and literacy skills in a variety of response formats provides both a more comprehensive picture of students' capabilities and a more likely gender-equitable assessment.