Morbidly obese subjects with airflow obstruction who underwent laparoscopic bariatric surgery appear to have the greatest risk to develop complications. In a retrospective cohort study, we identified a waist circumference >= 120 cm, smoking history >= 5PY and history of obstructive lung disease as statistically significant predictors of airflow obstruction. The resulting algorithm, aimed to identify subjects with airflow obstruction before bariatric surgery, was validated in a prospective study. The algorithm was found to be effective in identifying patients with low risk of airflow obstruction (negative predictive value 94.7%). Airflow obstruction, however, was not associated with post-operative complications as we expected. In contrast, inspiratory capacity and the Epworth Sleepiness scale were more promising predictors for post-operative complications in subjects undergoing bariatric surgery.