The nature of the message used by children, 4 1/2 and 6 1/2 year-old, was studied in a spatial description task. Speaker and listener were separated from one another by an opaque screen, and had to exchange information. Speaker were asked to describe a board showing eight objects placed in a room, and listeners were instructed to draw a similar picture on the basis of this description. The analysis of the message focused on the description of the object and the expression of spatial location. The results indicated the cognitive difficulty involved in having to distinguish referents according to the attribute and the use of grouping strategies. Although children's overall performance improved with age, the older group presented more messages of low informative quality related to objects that did not have a specific spatial frame of reference. These last results are discussed in terms of private speech that emerge when subjects' linguistic ability is insufficient to organise a complex cognitive situation. It appears that the cognitive features of the message play an important role both in the denotation of the referent and its spatial location.