The main goal of the dissertation was to compare the results of interpreting analog and digital CIR aerial photographs, as well as define the most reliable interpretation method for the assessment of tree health status for operational use by examining the best sample size and number of trees interpreted per sample.Analog and digital aerial photographs from two recording periods (1989 and 2008) were interpreted for a part of the management units Josip Kozarac and Opeke. At each point of a 100x100 m grid, 4 nearest trees (crowns) were estimated and damage indicators (damage-O, mean damage-SO, damage index-IO, mean damage1-SO1) were calculated for individual tree species, for all the interpreted species together, per surveying strips, and for the total research area.On the basis of calculated damage indicators obtained by interpreting analog and digital recording from 1989 and 2008, it was found that there was no statistically significant difference between the results in terms of tree health assessment, with the same sample size.The sample size was then tested at different densities of network points (200x200 m, 300x300 m, 500x500 m; 1000x1000 m), with different combinations of the number of trees interpreted per sample (1,2,4 trees). Different densities of sampling points and numbers of interpreted trees per sample were found to have a significant impact on the assessment of tree health status.A comparison was subsequently made of the results of field assessment of damage (ICP Forest) and the assessment of damage by interpreting CIR aerial photographs for the study area. The assessment of tree health status in analog and digital recordings was not found to differ significantly in relation to field assessment.The results obtained with the interpretation of CIR aerial photographs are also presented on thematic maps, which give an insight into the spatial distribution of medium and significant damage of stands in the study area.This research has established the most convenient method of interpretation for operational application. This method ensures sufficient statistical reliability of the assessment of tree health status in CIR aerial photographs, with the best sample size and number of interpreted trees. The existing methods of health status assessment have thus been improved and new possibilities of applying digital CIR aerial imagery in forestry have been presented.