Education has a long tradition in the use of illustrations of different types. The aims of the illustrations are to facilitate and to clarify for the pupils. But is that really the case? The topic of this study is to generate knowledge about how children make use of illustrations in mathematical textbooks in primary school. This study focus on seven-year-old pupils and the illustrations have delimited to the area of subtraction. Video observations from twelve pupils who, in pairs, discussed five selected illustrations were made. The empirical material was analyzed using affordances (Gibson, 1986) and subtraction situation (Fuson, 1992). Firstly out of the interaction between pupils and illustrations and secondly out of the two different subtraction situation: Change-take-from and Compare. The analysis of the video observations showed that the pupils sometimes discover the aimed subtraction situation and/ or affordance and sometimes not. This affects how pupils handle the mathematical operations. A conclusion of this was that pupils have to discover the aimed subtraction situation as well as the aimed affordance to be able to handle a mathematical operation in the textbook in a desirable way. The result also showed a number of variables that effected how the pupils made use of the illustrations, such as: the pupils own experiences, the amount of information the pupils interpreted in the illustrations and how the pupils defined when one illustration stopped and the next begun. Knowledge of this is of great importance for teachers as well as textbook authors and textbook illustrators, in order to create good conditions and support for the pupils during mathematics classes. We live in a visual world and the ability to read illustrations are today of great importance. What is more, the mathematics education is a textbook controlled subject. Little has been written about how pupils make use of illustrations in mathematics textbook, especially concerning younger children. This is therefore of great importance both in the Nordic area as the world at large.