Abstract Oscillating Water Column systems (OWC) have been in the spotlight in the last 20 years since these devices are considered one of the most promising devices among wave energy technology. These systems produce electricity by means a generator driven by a turbine, which takes advantage of the bidirectional flow created by the OWC itself. Among these turbines suitable for bidirectional flows, it is possible to find radial impulse turbines, which are the focus of this work. Traditionally, the radial impulse turbines have shown lower efficiencies than their competitors. However, the radial turbines present interesting mechanical features and, recently, some research show that the difference has been reduced. Following this thread, this work deals with another modification in the radial impulse turbine looking for a further improvement. By using a validated CFD model, it has been analysed the influence of the lean angle of the blade. Until now, all the turbines present in the literature are leaned zero degrees, leading to a strong interaction between the guide vanes and the blades. This work shows results of the same turbine, equipped with blades leaning from -5deg to 25deg, in order to determine the influence such a modification on the maximum total-to-static efficiency. Results have revealed a slight improvement in the maximum efficiency for positive leaning angles, whereas negative angles drive the turbine to worse performance.