-Modern technologies have changed the landscape of teaching and learning in many ways, including introduction of computational support for knowledge assessment. Concept maps (CMs) can be used to externalise student's internal knowledge structure in a form suitable for computer-aided assessment. Current CM-based knowledge assessment systems do not analyse semantics of CM elements. The paper represents a study designed to find out how big is the portion of a CM that is left unevaluated in default of semantic analysis.