Airborne Laser Scanning (ALS) has been widely used to survey forest areas. The extraction (segmentation) of individual trees from ALS point clouds is a prerequisite step for tree biophysical parameter estimation. For this purpose, we develop and evaluate a graph based segmentation algorithm adapted to deciduous forests scanned with high density LiDAR (~50 points / m2) in leaf-off conditions. The algorithm is applied to a 1 ha deciduous forest plot in western Switzerland and the accuracy of individual trunk locations is evaluated in terms of recall, precision and F-score. The results indicate that the algorithm performs satisfactorily within the experimental setup conditions.