Applying combined cross-sectional and longitudinal methodology, this study investigated how self-regulation develops in early adolescence, and whether that development is linear and similar for boys and girls. Baltes and colleagues (1990, 2002) operationalized self-regulation within the Model of selection, optimization and compensation. Participants were students from 4th to 8th grade in five primary schools in Zagreb. In the cross-sectional part of the research 720 adolescents participated (52% girls; average age 12.6 years), and in the longitudinal part a total of 382 adolescents (50% girls; average age 11.2 years at T1) were followed in three time points, over two years. To measure two self-regulatory processes, selection and restructuring, we applied Self-regulation vignettes, developed within the research presented here. Selection refers to the strategies of goal selection and restructuring refers to the usage of inner and external resources required for goal attainment. The results of cross-sectional and longitudinal analyses consistently show that both selection and restructuring decrease with age, and those girls have higher results than boys on the restructuring scale. In addition, we found that selection decreases linearly during early adolescence, following similar paths for boys and girls. Restructuring also decreases similarly for boys and girls, but the developmental trend is not linear - after decrease from forth to sixth grade, we found stagnation in the seventh grade and a new decrease in the eighth grade. We also reported results on congruent validity of the vignettes, the alternative measure of self-regulation. PUBLICATION ABSTRACT