Competencies have become a leading construct in human resource practices. However, empirical research on competencies has lagged behind resulting in a gap between practice and science. In this study, the focus was on the nature of competencies by examining the relationships of three competency dimensions with cognitive ability, personality and performance during assessment center exercises. Data of 932 applicants participating in a 1-day selection procedure were used. Results showed that to assess the competency dimension Thinking psychologists focus on cognitive ability. To assess the competency dimension Feeling psychologists rely on performance during interview simulation exercises and on measures of personality. In assessing the dimension Power psychologists focus mainly on personality, although they also rely on cognitive ability and performance during interview simulation exercises. © 2007 Blackwell Publishing Ltd.