Despite the large body of knowledge on adults suggesting that 2 basic types of mental spatial transformation--namely, object-based and egocentric perspective transformations--are dissociable and specialized for different situations, there is much less research investigating the developmental aspects of such spatial transformation systems. Here, an "own body transformation" paradigm and a letter transformation task were employed in a group of children ranging from 7 to 11 years of age to respectively investigate the development of egocentric perspective transformations and object-related transformations. A group of 30 young adults was also administered the 2 experimental tasks. Moreover, the Temperament and Character Inventory (Cloninger, Przybeck, Svrakic, & Wetzel, 1994) was also administered to children and adults with the goal of testing for possible influences of personality traits on imagined perspective transformation abilities. We found that egocentric perspective transformations develop later than object-based transformations--namely, from 8 rather than 7 years of age. We also found that high scores on temperament and character scales reflecting the acceptance of others (i.e., cooperativeness) were positively related to the ability to engage in imagined perspective transformations, especially when such ability first appears (i.e., at 8 years of age). These findings were held to support the view that the 2 mental spatial transformation systems are separated in that they follow 2 different developmental trajectories and are differentially influenced by personality traits in children.