Combustion aerosols and particle clusters are often analysed by transmission electron microscopy in order to characterize their morphology on the basis of the fractal dimension. We present a study that is focused on the determination of the mass and perimetric fractal dimensions with two different methods. An individual method relies on the study of a single aggregate at different scales whereas a collective method is based on a population of a large number of aggregates. We investigate the influence of many parameters like the image resolution, the aggregates roughness or their orientation on the determination of the fractal dimension as well as the carefulness required to correctly define the box size range in the individual method. (C) 2013 Elsevier Ltd. All rights reserved.