Background : To study any interference of demonstrated in different patient satisfaction scores for the same questionnaires handled by hospital staff and by independent surveyors, respectively. Methods : This study included 728 subjects who were admitted to a university hospital from June 22 to July 1, 1999. The contents of the questionnaire were composed of six dimensions: hospital structure and process, staffs technical competence and humaneness, information & education and communication. Measurements were performed on a 5-score Likert scale. T-test and logistic regression analysis were also performed. Results : In an outpatient survey, satisfaction scores from a questionnaire delivered by hospital staff were significantly higher than independent surveyors for the dimension of communication, but no differences were shown among other dimensions. In an inpatient survey, satisfaction scores by hospital staff were higher for the process and communication dimensions(p<0.05). In particular, in both the inpatient and outpatient surveys, the difference of satisfaction scores for personnel items were significant between groups. After adjustment for age and sex those differences were significant between groups. Conclusion : To minimize the bias on questionnaire survey, the effects of personnel, who deliver and gather the questionnaire should be carefully considered in the evaluation of health service satisfaction.