In two experimental and exploratory studies, we wanted to test the differentiated effects on preschoolers with externalizing behavior (EB) of two short-term social information processing (SIP) and Theory of Mind (ToM) training sessions, in comparison with typically developing (TD) preschoolers or with preschoolers with EB whom didn't receive training. Firstly, nineteen preschoolers presenting a high level of EB problems took part in a pre-test session involving direct cognitive and socio-cognitive measures (assessing the understanding of emotions, beliefs and social problem-solving). They were then allocated at random to two experimental groups (ToM or SIP training) and compared to nineteen TD preschoolers who followed the same procedure. Four experimental groups, EB-ToM group (n = 9), TD-ToM group (n = 9), EB-SIP group (n = 10), TD SIP-group (n = 10), received short training sessions, which were given by group of three children. All children took part in a post-test session. Secondly, EB-ToM group (n=9) and EB-SIP group (n = 10) was compared to a control group of preschoolers with EB problems (n = 9). These preschoolers took part in pre-test and post-test sessions. Firstly, we tested whether the effectiveness of the training was specific to children with EB compared to TD children. Although improvement was obtained in typically developing children, larger improvements were found in the population with EB. Secondly, we compared the potential transfer of learning between the two types of experimental training in children with EB problems. Results showed some improvement in ToM and in SIP for both experimental groups. These studies provide some guidelines for training in social cognition aimed at preschoolers who are at risk of or have developed EB disorders