The use of techniques based on spectral extinction to recover particle size distributions has become increasingly popular in recent years. However, they are time-consuming and are not always successful in practical applications. In this paper, a novel method is proposed to determine particle size distributions using neural networks from several spectral extinction measurements. Simulations and experiments have illustrated that it is feasible to use a neural network to obtain the parameters of a particle size distribution from turbidity measurements. Although the neural network was trained using log-normal distribution data, it can be used to recover some non-log-normal distributions. The method has advantages of simplicity of use, instantaneous delivery of results, and suitability for online particle size analysis.