BACKGROUND The 99mTc-exametazine labelled leukocytes (99mTc-WBC) scintigraphy is an established method for the inflammatory bowel disease (IBD) diagnosis, but the labelled procedure is a large and laborious process. The 111In-labelled human polyclonal immunoglobulin G (111In-IgG) can be an alternative in the non invasive IBD diagnosis. METHODS Thirty-four patients routinely referred for investigation of IBD were studied. The 99mTc-WBC and 111In-IgG were simultaneously injected and images were obtained at 30 min, 3 and 24 h post-injection. The diagnostic was established by histology of endoscopy and/or surgery samples. Images were blindly evaluated by two experienced observers who only knew of the clinical suspicion of IBD. IBD was confirmed in 27 patients (17 with Crohn's disease [CD] and 10 with ulcerative colitis [UC]). RESULTS Sensitivity, specificity and accuracy were 88.5, 100 and 90.3% respectively for endoscopy, 73.7, 75 and 73.9% for radiology, 59.3, 85.7 and 64.7% for 111In-IgG scan and 96.3, 85.7 and 94.1% for 99mTc-WBC scan. In the diagnosis of CD involvement of small bowel, the 99mTc-WBC scan identified 9/11 patients with confirmed disease, whereas the 111In-IgG scan diagnosed only four of them. In the evaluation of colonic disease, the 99mTc-WBC scan correctly diagnosed 21/22 confirmed patients, being the 111In-IgG scan positive in 13 of them. As far as disease extension concerned, the 99mTc-WBC demonstrated a statistically significance rather number of disease segments than endoscopy, radiology and 111In-IgG scan. CONCLUSIONS The 99mTc-WBC was an effective method in the diagnosis of suspected IBD patients, both in the evaluation of small bowel disease and colonic disease, with slightly best results for colonic disease, whereas the 111In-IgG scan seems to have no utility neither in diagnosis nor in extension evaluation of IBD.