Knowledge of patients' opinions and beliefs about their illness is fundamental in interdisciplinary health care interventions. The IPQ and its revised version (IPQ-R) are questionnaires designed to assess components of the mental representation of illness described in Leventhal's self-regulation model. To validate the IPQ-R in the Italian population, verifying its psychometric properties and focusing on Part II of the instrument (opinions about disease), we enrolled 277 inpatients (216 males and 61 females) affected by myocardial infarction (n=70), coronary artery by-pass graft surgery (n=52), chronic heart failure (n=47), valve replacement (n=20), obstructive sleep apnoea syndrome associated to obesity (n=53) and respiratory failure (n=35). All patients completed the Italian version of the IPQ-R obtained by means of 3 translations and a back version. IPQ-R scores were compared to patients' scores on the SF-36 and AD schedule (on anxiety and depression). Structural validity and reliability (both internal and test-retest) of the Italian IPQ-R were assessed. The validity of Part II of the IPQ-R was confirmed. As in the original version, 7 factors were extracted. ANOVA revealed statistically significant differences between the different diseases. Correlations between IPQ-R and, respectively, the SF-36 and AD schedule were statistically significant and coherent with the constructs analyzed. Finally statistically significant correlations emerged between the IPQ-R factors. The test-retest reliability and internal consistency of the questionnaire were confirmed. The psychometric properties of the Italian version of the IPQ-R were demonstrated to be robust. Hence, the Italian version of the IPQ-R, which resulted homogeneous with the original version, could be useful in assessing the cognitive factors involved in patients' adjustment to various chronic illnesses.