Drug attitude inventory (DAI-30) is considered to be the best predictor of poor adherence in first-episode schizophrenia. We compared the short version (DAI-10) with DAI-30 in long-term schizophrenia, documented if DAI was associated with poor insight, PANSS and GAF and constructed DAI-10 percentiles. DAI-30 and DAI-10 were homogenous (r = 0.82 and 0.72, respectively) with good test–retest reliability (0.79). The correlation between the DAI versions was high (0.94). Percentile scores of DAI-10 were computed. DAI is an easy-to-use self-report instrument seemingly assessing a unique clinical dimension relevant to non-adherence. DAI-10 might be preferred for its simplicity and good psychometric properties.