The study presents the results of a four-year long survey among pre-service teachers, examining factors which influence their knowledge and skills on computers, as well as factors which contribute to shaping their perceived computer competency. Participants were seven hundred fifty-four senior students, at the Department of Primary School Education, University of the Aegean. Results analyses, using multiple linear regression, indicate that pre-service teachers do not actually know much about computers and that they base their perceived competence on computers mainly on how skilled they believe they are in office applications. Results also indicated that the number of ICT related courses students attended contributed, to some extent, in knowledge acquisition but did not influence their perceived computer competency. Based on the results, recommendations are made in order/so as pre-service teachers to be more adequately prepared to meet the challenges of using ICT at school.