The paper presents the ideas of P.Ya. Galperin on the nature of moral behaviour and the basic patterns of internal responsibility in childhood and adolescence. Distinctive features of objective and subjective responsibility, internal and external responsibility are highlighted. It is argued that internal responsibility expresses the person’s attitude to society and social groups and might be developed only if involved in certain relations and implemented in socially useful activities, i.e. if it is significant for other people. The psychological roles of cooperation for of responsibility are compared in J. Piaget’s works and P.Ya. Galperin’s scientific theory. The research results of internal responsibility in primary school students and adolescents conducted by P.Ya. Galperin and T.V. Morozkina are discussed. The decisive role of value orientation and motivation in solving «affective type» problems and in moral behaviour is shown. According philosophy issues, responsibility is considered as a perceived necessity, which assumes a free moral choice. Three criteria of moral responsibility are introduced: the causal relationship between the subject’s behaviour and its consequence, subject’s ability to predict the possible consequences of his/her behaviour, the possibility of free choice. The psychological content of responsibility is the subject’s commitment and further response regulated by a certain system of norms and regulations on the basis of moral choice and self-regulation. The distinction between the action device and motive as the accepted moral basis for behaviour has been introduced. Accordingly, responsible behaviour is considered as willful behaviour. The genesis of strong-will behaviour is associated with social relations and moral values and is developed in the course of cooperation. Conditions of orientation in moral choice as a prerequisite for actualizing the individual’s internal responsibility are discussed.