This paper presents a process-structural model of the planning of drawings in childhood, and reports on seven experiments investigating children's ability to plan their drawings in advance. Three constructs are basic to the model: a figural scheme or schema, a spatial mental model, and a working memory called "M operator" or "central computing space" that increases in capacity with age. A specially designed drawing task was used that enabled researchers to study quantitative relations between capacity of working memory and ability to plan in advance. In the experiments, children were required to (1) think of an interesting scene to draw, (2) verbally describe the drawings they intended to make, (3) point out positions on white paper where elements of the drawing would be placed, and (4) draw. Subjects participated in either free or constrained versions of the task. In the constrained version, children were presented a list of items for inclusion in their drawings. Substantive findings were obtained in Experiments 3, 6, and 7. Involving 67 first graders and 90 fourth graders, experiment 3 provided a first test of the model and suggested a modification. Experiment 6, which dealt with 35 first graders, 45 third graders and 42 fifth graders, provided substantial support for the revised model. Experiment 7 provided additional control. It is concluded that the consideration of general information processing constraints on drawing skills is a promising approach. (A 10-page reference list, 14 reference notes, tables and figures are appended.) (Author/RH)