This study investigated the development of planning and its relationship with age and other cognitive processes taken from the PASS model. Ninety-nine students in grades two, four, and eleven were administered planning, simultaneous processing, successive processing, and attention tasks. MANOVA with grade level and gender as independent variables revealed that grade level had a significant effect on planning, whereas gender did not. All but one planning variable showed a significant main effect of grade in subsequent ANOVAs. Pair-wise comparisons between grade levels indicated that the developmental trajectories were not uniform in different tasks. Regression analyses indicated that the contribution of the other three cognitive processes to planning varied as a function of the specific planning task. The adequacy of different planning measures and the need for collecting verbal protocols while subjects are engaged in solving the problems are discussed.