Background: Inflammatory bowel disease (IBD) impairs health-related quality of life (HRQOL). Our aim was to investigate whether the improvement in the Clinical Activity Index (CAI) and Endoscopic Activity Index (EAI) is significantly correlated with the advancement of HRQOL and its dimensions in ulcerative colitis (UC) and to assess whether demographic and disease-related factors influence patients' experience of HRQOL. This examination was performed in the context of our recently published study of the anti-inflammatory effect of phosphatidylcholine in UC. Methods: Sixty patients with chronic active UC were treated with phosphatidylcholine or placebo over 3 months. They were asked to complete the Inflammatory Bowel Disease Questionnaire-Deutschland (IBDQ-D) before and after the study. The correlations between CAI and EAI and IBDQ-D scores were calculated. Demographic and disease-related factors were obtained. Results: A statistically significant lowering of CAI and EAI after treatment in the phosphatidylcholine group led to a statistically significant improvement in HRQOL (r = −0.623, P = 0.0003 for CAI; r = −0.511, P = 0.005 for EAI). Constant disease activity indexes in the placebo group accompanied constant HRQOL (r = −0.747, P < 0.0001 for CAI; r = −0.634, P = 0.0002 for EAI). Furthermore, besides a few exceptions, significant correlations between CAI and EAI and the 4 dimensions of the IBDQ-D could be shown. Demographic parameters did not significantly influence the IBDQ-D scores. Conclusions: This study points out the strong relationship between CAI and EAI and all domains of HRQOL in patients with UC. Therefore, the IBDQ-D is a valid and reliable assessment tool that reflects changes in the health status of UC patients. It is a useful measure of therapeutic efficacy and should be used in clinical trials in IBD.