The distribution parameter of the drift-flux model has been developed for a rectangular channel and a simulated boiling water reactor (BWR) subchannel. The void fraction prediction by the subchannel drift-flux code CANAL is well demonstrated for heated rectangular channels. Intrasubchannel flow and void profiles are considered for subchannel model development. Distribution parameter C0 is found to be very sensitive to variation of the geometric parameters and subchannel types. Since void fraction measurements corresponding to the rectangular subchannel of a BWR rod bundle are unavailable at present, assessment of the derived models remains to be performed.