Background: Despite being one of the questionnaires to assess anxiety more employed by mental health professionals, the State Trait Anxiety Inventory (STAI) has been criticized. The main criticism is that the possible existence of a set of items to assess depression would form an independent factor. Objective: The aim of this work is to evaluate the STAI factorization in a sample of patients diagnosed with depression. Method: We applied the Spanish adaptation of the STAI to 266 Spanish patients diagnosed with various depressive disorders. Results: Three underlying factors were identified in the exploratory factor analysis: state anxiety, positive trait anxiety and negative trait anxiety. Discussion and conclusion: The factorization did not confirm the presence of specific item sets for depression, pointed above as the main criticism of this questionnaire. Furthermore, the high values of the categorical alpha, both in the factor structure obtained and the theoretical subscales, are highly reliable indications for the use of the STAI in patients diagnosed with depression.