AbstractBackground: Receiving exact dose by the patients is vital in radiotherapy. The TECDOC1583 protocol is used to achieve this goal. This study aimed to evaluate several levels and steps of treatment planning, in order to calculate the precise dose received by the patient, and to compare it with actual results.Methods: The distribution of doses for single, multiple and complicated multiple field beams of treatment planning were calculated using TiGRT. Results were compared with the measured results of anthropomorphic phantom in different phases.Findings: According to the TECDOC1583 protocol, all the results were accepted; but in the fifth level of the test, percent of error in the lung was 4.3% which made a 0.3% of discrepancy. In the sixth level of the test, the percent of error in soft tissue was 5.7% with about 2.7% of discrepancy.Conclusion: Due to the lack of electronic density in lung tissue, a treatment planning software with higher accuracy is needed for evaluations. Our findings showed that technicians’ knowledge regarding to the application of treatment planning software is essential in this regard. Since the produced error would not be acceptable in this area, and the accuracy of the treatment planning software is no more confident, so working based on correct algorithm of treatment planning software should be checked and system restarting and commissioning must be re-evaluated periodically.