In this paper, we investigate the predominance of the linear model in 12-13 year old Cypriot students, while solving non-proportional word problems involving area and volume of rectangular figures. Using three different kinds of tests related to the context of the word problems presented we attempt to identify a differentiation in students’ responses. The results reveal students’ tendency to apply proportional reasoning in problem situations in which this kind of reasoning is not suited. This tendency appears to decrease in the second phase of the study when the context of the problems was changed. The data also suggest that students are not able to detect the common non-linear character of area and volume tasks and therefore, deal with them in a different way. (a, b, c, d), a b c d. Vol 3–23 Proceedings of the 28th Conference of the International Group for the Psychology of Mathematics Education, 2004 Vol 3 pp 345–352 3–346 PME28 – 2004 PME28 – 2004 3–347 3–348 PME28 – 2004 Note: Similarities presented with bold lines are important at significant level 99%. PME28 – 2004 3–349 3–350 PME28 – 2004 PME28 – 2004 3–351 Handbook of Research on Mathematics Teaching and Learning CHIC : Classification Hierarchique Implicative et Cohesitive-Version sous Windows – CHIC 1.2. Proceedings of the 25th Conference of the International Group for the Psychology of Mathematics Education Educational Studies in Mathematics, 50, Educational Studies in Mathematics, 35, Mathematical Thinking and Learning, 4 Learning and Instruction, 13(4), Mathematics as an educational task Didactical Phenomenology of Mathematical Structures Educational Research and Evaluation6(1) Learning and Instruction7 How students’ (mis-)understand science and mathematics: Intuitive rules. Proceedings of the 2003 Joint Meeting of PME and PMENA The Nature of Mathematical Concepts 3–352 PME28 – 2004