All guidelines on major depressive disorder (MDD) and anxiety disorders recommend pharmacotherapy and/or psychological treatment for moderate to severe disease. The aim of this cross-sectional study was to investigate treatment inadequacy, both pharmacological and psychological, in a large naturalistic cohort of subjects with MDD and anxiety disorders from the Netherlands Study of Depression and Anxiety. All subjects with a current 6-month diagnosis were included (n=1662). Demographic data, clinical features and actual medication use were assessed in face-to-face interviews. In moderate to severe MDD, 43% of the subjects were not treated sufficiently with antidepressants or psychological treatment. In primary health care patients, this undertreatment was 70%. In moderate to severe anxiety disorders, 44% of the subjects were not treated sufficiently with antidepressants, benzodiazepines or psychological treatment. Among antidepressant users with moderate to severe MDD, 21% of the pharmacotherapy was inadequate with respect to drug choice, dose and every day use. Undertreatment and pharmacotherapeutic inadequacy are common in moderate to severe MDD and anxiety disorders. Both are more pronounced in primary care than in specialized care. This may be partly due to differences in disease recognition and help seeking behaviour. (C) 2013 Elsevier Ireland Ltd. All rights reserved.