Developmental neuroimaging results have suggested a progression in focalization in functional activations from childhood to adulthood. The mechanisms underlying this process are thought to be an age-related decrease in activation extent as well as an increased magnitude in task-related areas. The present study aimed to evaluate these notions while controlling for confounders that may bias towards focalization. We used adolescent subjects in small age ranges. In addition, head motion corrections were incorporated in statistical analyses and regions of interest were identified for each participant separately to overcome inter-individual variability in anatomy and functional organization. Activation patterns of 13-, 17- and 21-year-old males were compared during the decision phase of a challenging and complex gambling paradigm. The BOLD amplitude enhanced with increasing age, modulated by task conditions. First, response amplitude during difficult, endogenous relative to exogenous decisions increased with age. This decision difficulty effect was most pronounced in 21-year-olds, both in areas associated with task execution and default mode areas. Second, deciding to pass as opposed to gamble exerted more effort in inferior frontal and parietal areas only by 13- and 17-year-olds. There was neither an age-related decrease in activation extent, nor any qualitative shifts in activated areas as suggested by the focalization hypothesis. These results suggest that although different age groups throughout adolescence engage similar brain areas during decision making, the response magnitude in these areas increases with age particularly during difficult task conditions, providing that confounding factors are controlled. (C) 2010 Elsevier Inc. All rights reserved.