This paper presents an automated, continuous method to determine wood pellet size distributions of larger and, hence, representative samples based on 2D-digital image analysis. The analysis routine developed combines several image processing steps to detect and separate the respective particles. The test unit designed allows length determination of up to 140 kg of pellets with a rate of 10.2 kg/h without any manual intervention. Pellets with a diameter up to 10 mm and a maximum length of about 50 mm can be analysed. In addition, the amount of fines is detemiined gravimetrically. Verification tests confirm an average standard deviation of 0.42% for the effective pellet length. First measurements of various pellet types show significant differences in their initial size distributions. The method developed provides a tool, which allows a more precise quality control of wood pellet size distribution. (C) 2020 Elsevier B.V. All rights reserved.