Background: Although hospital-based outpatient quick diagnosis units (QDU) are an increasingly recognized cost-effective alternative to hospitalization for the diagnosis of potentially serious diseases, patient perception of their quality of care has not been evaluated well enough. This cross-sectional study analyzed the perceived quality of care of a QDU of a public third-level university hospital in Barcelona. Methods: One hundred sixty-two consecutive patients aged ≥ 18 years attending the QDU over a 9-month period were invited to participate. A validated questionnaire distributed by the QDU attending physician and completed at the end of the first and last QDU visit evaluated perceived quality of care using six subscales. Results: Response rate was 98%. Perceived care in all subscales was high. Waiting times were rated as 'short'/'very short' or 'better'/'much better' than expected by 69-89% of respondents and physical environment as 'better'/'much better' than expected by 94-96 %. As to accessibility, only 3% reported not finding the Unit easily and 7% said that frequent travels to hospital for visits and investigations were uncomfortable. Perception of patient-physician encounter was high, with 90-94% choosing the positive extreme ends of the clinical information and personal interaction subscales items. Mean score of willingness to recommend the Unit using an analogue scale where 0 was 'never' and 10 'without a doubt' was 9.5 (0.70). On multivariate linear regression, age >65 years was an independent predictor of clinical information, personal interaction, and recommendation, while age 18-44 years was associated with lower scores in these subscales. No schooling predicted higher clinical information and recommendation scores, while university education had remarkable negative influence on them. Having ≥4 QDU visits was associated with lower time to diagnosis and recommendation scores and malignancy was a negative predictor of time to diagnosis, clinical information, and recommendation. Discussion: It is worthy of note that the questionnaire evaluated patient perception and opinions of healthcare quality including recommendation rather than simply satisfaction. It has been argued that perception of quality of care is a more valuable approach than satisfaction. In addition to embracing an affective dimension, satisfaction appears more dependent on patient expectations than is perception of quality. Conclusions: While appreciating that completing the questionnaire immediately after the visit and its distribution by the QDU physician may have affected the results, scores of perceived quality of care including recommendation were high. There were, however, significant differences in several subscales associated with age, education, number of QDU visits, and diagnosis of malignant vs. benign condition.