Emotional problems such as depression, anxiety and diabetes-specific distress are common in patients with type 2 diabetes mellitus (T2DM) but often remain unrecognized and thus untreated. The present Review focuses on the extent of this problem and discusses whether we should screen for depression, anxiety and diabetes-specific distress in patients with this condition. Depression has received by far the greatest attention from researchers. Strong evidence exists that depression affects 10-20% of patients with T2DM, but it is often unrecognized. Several guidelines have therefore recommended periodic assessments of emotional well-being in patients with T2DM. However, this recommendation is not based on strong evidence, as the effects of screening (case-finding) on psychological outcomes and diabetes outcomes have not been tested in a randomized controlled study. Results from studies in patients without T2DM have shown that screening for depression does not improve outcomes. On the other hand, collaborative care approaches for depression in patients with type 1 diabetes mellitus (T1DM) or T2DM seem to be effective. Intervention studies for anxiety or diabetes-specific emotional distress are currently lacking, and further research that can help to optimize antidepressant treatment is also urgently needed.