The laser measurement technique based on the ratio between the laser induced fluorescence (LIF) and the scattered light (Mie) intensities of droplets is presently limited to the evaluation of the Sauter mean diameter of the droplets. The important measurement of the droplet size spread is currently missing. An extension of the LIF/Mie technique for the measurement of droplet size spread is proposed here and is evaluated numerically. The method is based on the imperfect relationships between the scattered light intensity and the droplet surface area or the fluorescent light intensity and the droplet volume, which convey additional information that can be used to evaluate the droplet size spread.