BACKGROUND The armed conflict in Colombia is considered one of the most violent in Latin America. Children as a vulnerable population are most affected, increasing their risk of developing mental problems such as anxiety disorder and post-traumatic stress disorder. OBJECTIVE To determine the prevalence of the most frequent mental problems in the Colombian children affected by armed conflict. METHODS A cross-sectional study, using data from the National Mental Health Survey 2015. With children aged 7 to 11 years, in whom the RQC, PCL and DISC-IV-P (3.0.1) were applied. RESULTS We described information on 100 displaced children between 7 and 11 years old due to armed conflict, being a representative sample at national level. It was found that 98.7% of this population is at school, as well as 17.8% in poverty. Mental illnesses were asked according to their appearance in the last 12 months, these were: anxiety disorder 6.5% (CI 95% 2.7-14.7) in displaced population, compared to 1.8% (CI 95% 1.1-3.1) in non-displaced; High score for post-traumatic stress was 13.2% (CI 95% 3.9-36.4) in displaced persons and 6.6% (CI 95% 4.0-10.7) in nondisplaced persons. CONCLUSIONS Children affected by armed conflict have greater risk of presenting some mental illnesses such as anxiety disorder and post-traumatic stress, evidencing the situation of vulnerability in which they are.