Aim: to conduct a comparative analysis of the psychological characteristics of the most and least successful main control room operators. Material and Methods. Two NPP staff groups: the most and least successful main control room operators, who worked in routine operating conditions, were surveyed. Expert evaluation method has been applied to identify the groups. The subjects were administered the Minnesota Multiphasic Personality Inventory (MMPI), Cattell's Sixteen Personality Factor Questionnaire (16PF form A) and Raven's Progressive Matrices test. Results. Numerous significant psychological differences between the groups of most and least successful control room operators were obtained: the best operators were significantly more introverted and correctly solved more logical tasks with smaller percentage of mistakes under time pressure than worst ones. Conclusions: 1. The psychodiagnostic methods used in the study were adequate to meet research objective 2. Tendency to introversion, as well as developed the ability to solve logic problems undertime pressure, apparently, are important professional qualities for control room operators. These indicators should be considered in the process of psychological selection and professional guidance of nuclear power plant operators.