BACKGROUND The construction of a colostomy is a common procedure, but the evidence for the different parts of the construction of the colostomy is lacking. Parastomal hernia is a common complication of colostomy formation. The aim of this study is to standardise the colostomy formation and to compare three types of colostomy formation (one including a mesh) regarding the development of parastomal hernia. METHODS Stoma-Const is a Scandinavian randomised trial comparing three types of colostomy formation. The primary endpoint is parastomal herniation as shown by clinical examination or CT scan within one year. Secondary endpoints are re-admission rate, postoperative complications (classified according to Clavien-Dindo), stoma-related complications (registered in the case record form at stoma care nurse follow-up), total length of hospital stay during 12 months, health-related quality of life and health economic analysis as well as re-operation rate and mortality within 30 days and 12 months of primary surgery. Follow-up is scheduled at 4-6 weeks, and 6 and 12 months. Inclusion is set at 240 patients. CONCLUSIONS Parastomal hernia is a common complication after colostomy formation. Several studies have been performed with the aim to reduce the rate of this complication. However, none are fully conclusive and data on quality of life and health economy are lacking. The aim of this study is to develop new standardised techniques for colostomy formation and evaluate this with patient reported outcomes as well as clinical and radiological assessment. BACKGROUND Clinicaltrials.gov, NCT01694238.2012-09-24.