First results of raindrop size measurements obtained by two instruments whose operation principles are basically different are presented and the necessary procedure of comparison is described. The two devices are (i) a disdrometer which converts the mechanical momentum transferred by hydrometeors to a sensible surface into an electrical signal which allows a quantitative size classification and (ii) a Malvern Particle Sizer evaluating the particles' sizes in a specific volume by laser diffraction. The results differ in the range of small drop sizes, for large drops the agreement is quite good. Possible reasons for the differences are discussed.