" Social welfare " and " social problems " should be considered as two sides of one coin. In this paper, the concept of " social problem " is defined, through reviewing four textbooks, as a situation which is considered as a threat for quality of life or vital values by a considerable number of population but, of course, not necessarily the majority of them. In addition, this situation should contain some social causes or effects and its abolition should require some changes in social policies. Accordingly, poverty, inequality, social deviation, and difficulties in social institutions, i.e. production, administration, general health, mental health, education, and family can be categorized as typical social problems. Functionalist, conflict, and interactionist theories explain social problems differently, and therefore, propose different policies to resolve them. Whereas functionalists considere social problems as those who have arised out of a disrupture between norms and behaviors, conflict theorists regard them as products of an unjust distribution of power, wealth , status, and information . These macro theories do not explain the individual differences in a given social condition this is relinquished to interactionists who emphasize the semantic and interpretive processes, such as labelling and differential assocation as forces on individual to deviate.