In the first part of this paper we discuss the feasibility of using Generalizability (G) Theory to examine the dependability of concept map assessments and to design a concept map assessment for a particular practical application. In the second part, we apply G theory to compare the technical qualities of two frequently used mapping techniques: construct-a-map with created linking phrases (C) and construct-a-map with selected linking phrases (S). We explore some measurement facets that influence concept-map scores and estimate how to optimize different concept mapping techniques by varying the conditions for different facets. We found that C and S were not technically equivalent. The G coefficients for S were larger than those for C. Furthermore, a D study showed that fewer items (propositions) would be needed for S than C to reach desired level of G coefficients if only one occasion could be afforded. Therefore, S might be a better candidate than C in the large-scale summative assessment, while C would be preferred as a formative assessment in classroom.