UML has gained industry recognition as a standard Object-Oriented systems development modeling language. Nevertheless, UML has been criticized for such deficiencies as semantic inconsistencies, vagueness, and conflicting notations. In the context of learning UML, difficulties that users face are frequently attributed to these shortcomings. However, empirical proof of such an attribution is missing. The relationship between the deficiencies inherent in UML and the difficulties in the learning process is the focus of this study. The concept mapping technique is used in this study to unveil the issues and concerns novice designers encounter when learning UML. The findings are reported and suggestions for alleviating the difficulties in learning UML are discussed.