AIM: To study the psychometric properties of the Positions on Nursing Diagnosis (PND) scale. BACKGROUND: The PND is a scale to measure nurses' attitudes toward nursing diagnosis. In previous studies, reliability of the scale was supported but its construct validity is still unclear with studies reporting both one-factor and three-factor models. METHODS: A cross-sectional study was conducted with a convenience sample of 262 nurses enrolled from one general public hospital and three long-term care facilities in Italy. Construct validity was assessed with confirmatory factor analysis. Criterion and contrasting-group validities were tested, as well as internal consistency reliability. RESULTS: Confirmatory factor analysis showed the adequacy of a one-factor model of the PND scale. Criterion and contrasting-group validities were supportive, as was internal consistency reliability. CONCLUSIONS: The PND is a valid and reliable scale to measure nurses' attitudes toward nursing diagnosis. Its use in practice and research is recommended.