This communication discusses styrene removal in air by positive and negative DC corona discharges. Experiments were performed with a wire-plate reactor and under a gas flow rate of 305 m3/h. In terms of averaged applied voltage and corona current, it is observed that the maximum negative corona current is always at least two times larger than the positive one at the same voltage level. At the same corona discharge energy density, however, the positive corona discharge produces around 2–6 times more ozone in comparison with the negative corona. For styrene removal, the positive corona processing is also around 2–6 times more effective than the negative corona. Humidity, an important and variable component of ambient air, affects the positive corona processing significantly. But it exerts a moderate effect on the negative corona. The differences between positive corona and negative corona discharges are attributed to their different discharge properties.