This study has two objectives: 1) to carry out a comparative exploration of empathy and a set of socio-emotional variables in childhood and adolescence, analyzing gender differences; and 2) to analyze the relationship of empathy with social behaviour, sociometric choice of prosocial classmate, self-concept and capacity for analyzing negative emotions in children and in adolescents. The sample is made up of 313 participants aged 10 to 14 years. The methodology used is descriptive and correlational. In order to measure the variables, we administered 12 assessment instruments. The ANOVAs indicate that, for all ages, girls score significantly higher in empathy, prosocial behaviour, assertive behaviour and ability for cognitive analysis of negative emotions, whereas boys present more aggressive behaviours in their interaction with peers. Furthermore, the analysis reveals that capacity for empathy does not increase between the ages of 10 and 14. Pearson coefficients suggest, for all ages, a positive association of empathy with positive social behaviours (prosocial, assertive, consideration for others), self-concept and ability to analyze the causes of negative emotions; and a negative association with negative social behaviours (aggressive, antisocial, withdrawal).