Purpose: In recent years a significant number of intellectual capital (IC) metrics has been developed and applied in many organizations. However, there is still a strong need to specify the relations among the different categories of intellectual assets that exist in the context of small to medium-sized enterprises (SME), and to determine the way these assets affect financial performance. This paper has a dual scope; first, to specify these relations, and, second, to explore the impact of IC on corporate performance. Design/methodology/approach: Hypotheses are tested through a survey conducted on Greek knowledge-intensive SMEs of the service sector. Firms' perceptions regarding intellectual capital categories, which were measured through the answers given on a structured questionnaire, and accounting data gathered from financial databases were combined. Findings: The findings indicate that the interaction of certain categories of intellectual assets in SMEs is in some aspects different from the pattern evidenced in other surveys that analyze large companies. Also, the empirical data provides supportive evidence that certain categories of intellectual capital positively contribute to corporate performance. (Contains 2 figures, 7 tables and 3 notes.)