Purpose: Although complicated sigmoid diverticulitis is the most common reason for laparoscopic sigmoidectomy, the level of evidence for preference of the laparoscopic approach is low. Methods: A multicenter, randomized clinical trial comparing laparoscopic and open sigmoidectomy for diverticulitis was conducted to evaluate the short- and mid-term outcome after both techniques. Data were assessed from randomized patients and from patients who refused randomization. Results of the here presented interim analysis describe the difficulties in randomization leading to abortion of recruitment. Results: 149 patients were enrolled in the randomized trial within 36 months until the interim analysis. A further 294 nonrandomized patients who preferred one of both surgical approaches were assessed. Several differences between these groups were apparent including simple epidemiological characteristics such as age (65 vs. 60 years, p < 0.001), gender (65% vs. 55% female, p = 0.05), BMI (27 vs. 26 kg/m, p = 0.01), and ASA class < III (72% vs. 87%, p < 0.001). Conclusion: The majority of eligible patients refused a random allocation. A widespread presumption of the advantages of laparoscopic surgery was probably the main reason for refusal. Patients participating in randomization did not reflect the general population in recruiting hospitals. Future trials comparing minimal invasive procedures should be conducted before presumptions concerning the outcome are widespread in the general population.