The intragastric balloon is a temporary treatment for obese patients. Fluid-filled devices have shown efficacy and safety, and are widely used. Recently, although there are no comparative studies between them, an air-filled balloon, Heliosphere® bag, has been proposed. Prospective, double-blind study in 33 patients with morbid and type 2 obesity: 23 female, 43.9±10 years, 120.3±17 kg, and body mass index (BMI) of 44.2±5 kg/m2, placing 18 gastric balloons filled with 960 cm3 of air (Heliosphere® bag) or 15 balloons filled with 700 ml of saline (Bioenterics-BIB®). Both balloons were placed with conscious sedation and removed under general anesthesia 6 months later. Intravenous drugs were given to control symptoms for 48 h. Patients were sent home on a 1000-kcal diet, multivitamin supplements, and oral proton pump inhibitors, and were followed monthly. Complications, symptoms, weight, and quality of life evaluated by the Gastrointestinal Quality of Life Index (GIQLI) scale were recorded. At 6 months, mean weight loss (12.8±8 vs 14.1±8 kg), BMI loss (4.6±3 vs 5.5±3 kg/m2) and percent excess weight loss (27±16 vs.30.2±17) showed no significant differences between both groups. At removal, two Heliosphere® bags were not found in the stomach, and four patients required extraction of the balloon by rigid esophagoscopy or surgery (p=0.02). Tolerance was good in both groups, but early removal occurred in three BIB® (20%) due to vomits and dehydration. The GIQLI total scores remained unchanged. Both balloons achieve a significant weight loss with good tolerance in obese patients. Nevertheless, Heliosphere® bag has severe technical problems that need to be solved before recommending it.