We calculate the confined exciton energy of zincblende GaN/BN cylindrical nanowires using a two-parameter variational approach within the effective mass approximation. Feasibility of light emission in the 300-700 nm range is attained, depending both on the nanowire radius and the graded interface thickness. It is shown that in actual zincblende GaN/BN nanowire samples, the existence of non-abrupt interfaces can blue shift the exciton recombination energy up to similar to100 meV for non-abrupt interface thickness of just a few monolayers. (C) 2004 Published by Elsevier B.V.