In this thesis experts’ diagnostic judgment formation is seen as a social cognitive process: It is analyzed as a person-related judgment and is investigated according to the social cognition paradigm. The theoretical foundation is provided by dual process models (e.g. continuum model), which assume two different strategies of person-related information processing in order to form a judgment. The heuristic strategy is characterized by a categorization process and the corresponding activation of a specific person category. The information integrating strategy focuses on individual characterization of a person and the corresponding collection and integration of individual person attributes. A judge’s expertise is acknowledged to have an essential influence on the process of judgment formation. Experts, in contrast to laymen, are able to switch between the two strategies. The degree to which diagnostic judgment formation can be described by means of dual process models is investigated in a series of four quasi-experiments including psychotherapists and teachers as experts and students and staff members of Saarland University as laymen. Thus, social judgment formation is compared in two different domains. Two experiments focus on judgment itself by measuring judgmental data. The two other experiments focus on attention allocation and person memory by measuring self-paced reading time and free recall. Results show the expected pattern in both professional domains. Both psychotherapists and teachers are able to switch between the two strategies. So experts’ diagnostic judgment formation can be described by means of dual process models.