A method and a system for jetting droplets of viscous medium, such as solder paste, onto a substrate, such as an electronic circuit board. The volume of the droplets are adjusted by regulating the amount of viscous medium that is fed into a jetting nozzle for subsequent jetting of the viscous medium droplets therefrom. The exit velocity of the jetted droplets is adjusted or maintained substantially constant by regulating the velocity with which the viscous medium is impacted. Furthermore, the rate at which viscous medium is fed, for instance by a feed screw, into the nozzle is adjusted in order to regulate the feeding time required for feeding the viscous medium into the jetting nozzle, for instance in order to maintain a constant feeding time.