A material of eight individual mature stands of different sizes and shapes and with different types of neighbouring stands was used to assess the effect of erroneous placement of stand boundaries by photointerpretation on the estimated area of individual stands. The boundaries of the eight stands were classified into three different groups according to the length of the shadows caused by the trees in the mature stands along the boundaries. Different distributions of errors in stand boundaries were assigned to the three groups of boundaries. By means of Monte Carlo simulation of errors in each boundary, the placement of each boundary was altered according to a normally distributed random deviate. New stand polygons were created and their areas were estimated. A total of 850 independent areal estimates was produced for each of the eight stands. The difference between mean area of the simulations and true area ranged from −1.3% to −9.6% of true area. The standard deviation for the simulated area ranged from 1.5% to 9.0%.