This study was designed to investigate the effects of propofol, sevoflurane and position changes on respiratory mechanics. Forty patients scheduled for thyroid surgery were divided randomly into two groups; those receiving sevoflurane (group S) (n=20), and those receiving TIVA propofol (group P) (n=22). Dynamic compliance (Cdyn), peak inspiratory pressure (PIP), and respiratory resistance (Rr) values were recorded with a VenTrak respiratory monitor (Novometrix Inc. USA) at three time instances. The first measurement was done immediately after the beginning of ventilation and before the inhalation agent was initiated (Induction). Second measurement was done after 5 minutes of thyroid position (Thyroid) (ventilation with 1 MAC sevoflurane concentration or propofol infusion at the rate of 6 mg/kg/h). The third measurement was performed 5 minutes after end of surgery in the supine position (Supine) Blood gases were measured at the three time instances. Respiratory mechanics did not change in the P group (51±13, 46±11, 48±10 mL/cmH2O) at Induction, Thyroid and Supine positions). In the S group, dynamic compliance measurements showed changes statistically significant in the supine position (52±6 mL/cmH2O)) when compared to Induction (47±9 mL/cmH2O) and Thyroid position (47±6 mL/cmH2O) measurements (p<0.05). When the groups were compared with each other, there was no significant difference whatsoever at all periods (p>0.05). His concluded that sevoflurane, propofol and position changes exhibit similar effects on respiratory mechanics and blood gases at described dose and concentration.