Submucosal lifting of lesions prior to endoscopic resection is crucial to reduce complications and improve the technical feasibility of the procedure. To compare a self-assembled hydro-jet system vs. standard needle injection for tissue elevation prior to endoscopic resection of colorectal lesions. Randomised study performed at a single tertiary care institution. Consecutive patients with colonoscopic diagnosis of sessile polyps or non-polypoid lesions >5 mm or laterally spreading tumours. successful elevation, time to proper elevation, completeness of excision, cautery damage, and general histological diagnostic quality (blinded pathologic assessment). 79 patients were randomised to hydro-jet (40 patients, group A) and needle (39 patients, group B) elevation. Successful elevation was achieved in 97.5% and 94.8%, respectively. Time to proper elevation was 8+/-5 s vs. 18+/-3 s (p<0.05). In group A, histology showed selective accumulation of fluid in the submucosa with intact collagen fibres. Damage to muscularis mucosa was never noted in the specimens of group A and in 7 cases of group B (p<0.01). Artefacts from "cautery effect" were very limited. Radial margins of resection could be adequately evaluated in all cases and were negative. The hydro-jet system is as effective and safe as standard needle injection for tissue elevation prior to endoscopic resection of colorectal lesions, but it is significantly faster.