In this study, students’ understanding of chemical changes was investigated in relation to four individual differences, related to logical thinking, field dependence/independence, convergence and divergence thinking. The study took place in Greece with the participation of students (n=374) from three grades (8th, 10th and 12th grades) of secondary education. A stepwise multiple regression analysis revealed that the above cognitive variables were statistically significant predictors of the students’ achievement, with logical thinking to be the most dominant. Unexpectedly, no statistically important effect was found across ages. Moreover, students' partial achievement scores on understanding the structure of substances and their changes, along with the cognitive variables, appeared to have an effect on their competence in interpretation of chemical changes. Path analyses were implemented to depict these effects. A theoretical analysis that associates the role of cognitive variables with the nature of mental tasks involved when learning chemistry is also presented. Implications for science education are discussed.