The current work presents a study of an air blast simplex atomizer which supplies air to the fuel spray through radial channels for liquid film dispersing. The performance of two atomizer configurations using either co-rotating or counter-rotating liquid and air flows was investigated. The change in the direction of liquid swirl was achieved by replacing the inner swirler with a similar one having the holes drilled on the opposite side. Atomizer flow number FNSI in the experiments was 0.74·10−7. The study has shown that droplet size reduces significantly when the air velocity grows up to 60 m/s but further increase in air velocity has almost no effect on the droplet size. In the absence of air supply the increase in liquid pressure leads to the decrease of Sauter mean diameter (SMD) of droplets from 85 to 60 μm. However, in the air blowing regime the liquid pressure has only slight effect on SMD rising it from 30 to 40 μm. Better atomization performance has been obtained in the case of co-rotation atomizer.