Most analyses of cooling tower operation performed so far are based on calculation of characteristic number NTU [1, 2]. The towers themselves are considered as "black-boxes" and their operation is only the evaluated as "good" or "bad". To locate particular regions of cooling tower where the operation is unsatisfactory, additional measurements are needed. These include temperatures and velocities of the airflow over the entire surface above drift eliminators. Measurements show non-uniformity of heat transfer rate and airflow resistance over the cooling tower area. To determine influence of these non-uniformities to the airflow over the entire cooling tower height numerical simulations of airflow through a cooling tower were performed. Commercial software was used for the simulations. Additional models based on measurement results were included to describe heat transfer and airflow resistance through fill system. Numerical simulation gives temperature and velocity distribution within the entire cooling tower.