We constructed and calibrated an instrument targeting conceptual and procedural fraction knowledge. We used this instrument in a quantitative study with 126 secondary students (7th and 9th graders), testing the hypothesis that there are individual differences in the way students combine the two types of knowledge. Cluster analysis revealed four distinct student profiles: Students who were either stronger or weaker than expected with respect to both types of knowledge; students who were stronger with respect to conceptual knowledge; and students who were stronger with respect to procedural knowledge. These findings support the individual differences hypothesis. [This paper was published in: E. Bergqvist, M. Österholm, C. Granberg, & L. Sumpter (Eds.). "Proceedings of the 42nd Conference of the International Group for the Psychology of Mathematics Education" (Vol. 2, pp. 147-154). Umeå, Sweden: PME.]