Since time immemorial, placebos have been used in the treatment of patients with very different diseases. Interest in these substances has recently been renewed, since the use of placebo-controlled clinical trials has become the most useful tool to demonstrate the efficacy of a particular drug in patients with specific diseases. In inflammatory bowel disease (IBD), both in Crohn's disease and in ulcerative colitis, highly significant results have been obtained in patients in the placebo arm of clinical trials, surpassing even those achieved with drugs in other studies. Patients with IBD show certain characteristics that make them especially susceptible to the placebo effect: IBD are chronic diseases occurring in flares and pain is one of the main symptoms. In future, the placebo effect should be adequately quantified in the distinct clinical scenarios of IBD in order to design clinical trials that could demonstrate the true efficacy of the treatments investigated.