The majority of the research on additive problems has revealed two kinds of obstacles: the first is related to the position of the data in the scenario described by the text stating the problem and, second, to the distinction between positive or negative transformations of the data. This paper presents a large scale research about the difficulties in solving additive problems and the role of pictures in this kind of problem solving. In particular, we examine the case of the second class of additive structure problems proposed by Vergnaud: measure-transformation-measure or change problems. We have proposed to 1447 pupils of Primary Schools (grade 1 to grade 3) in Cyprus problems in verbal expression or in verbal expression accompanied with an informational picture. The analysis of the results based on the implicative statistical analysis proves that there is an influence of the type of representation and of the structure of the problem on problem solving. We discuss the theoretical and didactical implications of the findings of this research.