In addition to the actual semiconductor components and the cooling solutions required to dissipate losses, passive components account for a large part of the volume of power electronic converters. This publication presents methods for optimising the volume or occupied PCB board area of the passive components of current source inverters (CSIs). For this converter topology, these are primarily composed of the filter capacitors placed on the output terminals and the DC link inductance acting as the main energy storage device in the DC link. Design equations for the design of these components are presented first. In addition to the basic relationships for determining the capacitance or inductance of the respective components, other constraints for their design are also taken into account. Furthermore, an optimisation process is given for both the filter capacitors and the DC link inductance, with which the volume or the occupied board area of the respective components can be designed as small as possible. On the basis of the optimisation results for various input parameters, analytical relationships are then determined that can be used to quickly and easily estimate the volume and area at the beginning of a converter design process.