The aim of this study was to compare the performance of a new one-piece closed ostomy bag, SenSura, to an already established bag with a focus on minimizing problems related to use of stoma bags for individuals with a colostomy. There were 68 Danish participants with a colostomy who tested each bag for 1 week in a randomized, open, comparative, crossover study. The SenSura bag was perceived more secure than the reference bag (p=0.0006). Crucial performance and safety parameters were rated significantly better for SenSura than for the reference bag. The high preference for SenSura (85%) reflected these results (p<0.0001). Individuals with a colostomy can expect a higher sense of security with the SenSura bag than with the reference bag. This may relate to good adhesion, tack, flexibility and effective filter performance. Future studies should examine the long-term effects of SenSura on peristomal skin conditions. To our knowledge, this is the first published comparative study of one-piece closed ostomy bags.