An apparatus, method and computer program product for controlling flushing in rock drilling, and a rock drilling rig. The apparatus includes a control unit and a computer program for controlling feeding of a liquid component in an air mist flushing system in response to detected penetration rate of executed drilling. An operator may set a desired moisture target value for drilling cuttings removed from a drill hole and the control system automatically adjusts the flushing system to control the feeding of the liquid component.