In this work a method is presented to acquire 3D size information on particles in suspension. An experimental setup capable of acquiring two images from the same particle at different angles is presented. These images are then processed to yield a 4D measurement called axis length distribution (ALD). Using a measurement model and a restoration algorithm, the 3D particle size distribution (PSD) is reconstructed. The technique is applied to characterize the 3D PSD of ascorbic acid crystallized from methanol and Of beta L-glutamic acid crystals in water. The shape of these particles determined by the algorithm was found to compare well with observations from electron microscopy images. (C) 2009 Elsevier Ltd. All rights reserved.