We examine schoolchildren’s reasoning with spatial relations, such as ‘is to the left of’. Our aims are to obtain a more precise account of the effect of working memory on reasoning, a more detailed understanding of the internal representation of mental models and a developmental perspective. We discuss two experiments in which 348 children, between eight and twelve years old, needed to verify conclusions for 24 reasoning problems describing the spatial relations between pieces of clothing. In both experiments, children in the experimental condition were allowed to take notes by means of paper and pencil. In both experiments we find that the participants spontaneously draw iconic representations of the items’ spatial ordering, have a strong preference for only considering one possible state of affairs even when more are relevant, and that an explanation in terms of working memory capacity alone cannot fully explain the data.