There are anecdotal indications that students avoid questions involving time-dependent exam problems in quantum mechanics. To obtain real evidence a diagnostic questionnaire has been created and administered to third-year students. It measures students' understanding of quantum mechanics in general with an emphasis on misconceptions and threshold concepts that may block a deeper under-standing of quantum mechanics especially of time-dependent aspects. The questionnaire consists of two parts a self-evaluation section followed by a conceptual survey. Analysis of the results of this questionnaire does indeed reveal areas of weakness in student understanding of time-dependence as well as of other fundamental quantum mechanical concepts. The questionnaire has been revised in light of the analysis with the aim of improving the understanding of student difficulties as well as the reliability of the questionnaire itself.
