Until the end of the nineties last century personality disorders could not be diagnosed before the age of eighteen. Nevertheless, the results of studies published in the last decade have revealed that personality disorders can be observed in children and adolescents and that personality disorders diagnosed in adult patients had been present as early as in childhood. The knowledge of possible mechanisms shaping personality disorders in childhood is unsatisfactory and needs to be expanded. Developmental psychology explains the development of abnormal personality through inappropriate attachment patterns and abnormal transitions between developmental phases. Genetic and temperamental factors are also important in the aetiology of personality disorders as well as early maladaptive schemas resulting from personal experiences and interactions with others. The aim of this article is to review the current knowledge on the mechanisms shaping the development of personality and personality disorders in childhood and adolescence.