This study investigated Greek high school students' intentions and motivation towards and against pursuing academic studies in Computer Science (CS), the influence of the family and the scholastic environment on students' career choices, students' perceptions of CS and the Information Technology (IT) profession as well as students' attendance at CS courses at school, computer use in the home and self-efficacy beliefs regarding computers. Gender differences were examined with a view to identifying factors that may affect boys' and girls' career choices. The participants were 358 students of both sexes who completed an anonymous questionnaire. The data analysis showed that girls are less likely than boys to pursue a CS degree, and when they do so, it is mainly because of extrinsic reasons rather than personal interest in CS. Lack of opportunities for early familiarization with computing in the home and the scholastic environment is the factor that mainly differentiates boys' and girls' motivation against studying CS, having a greater impact on girls. Misconceptions of CS were detected in students of both genders. Girls view CS as a self-referencing, machine- and programming-oriented discipline to a greater extent than boys do, and hold less positive views of the IT profession. Boys view CS as more human- and application-oriented than girls do. They also have greater computer self-efficacy and more sex-stereotypical views of CS and IT as male domains. Appropriate actions to increase girls' interest and participation in CS studies are proposed according to the findings.