Surgery remains the treatment of choice for patients with certain lung diseases. One lung anesthesia is relatively indicated in such patients to facilitate surgical exposure and reduce operative time, the management of some problematic patients having thoracic surgery remains one of the most difficult challenges for the anesthesiologist. The effect of one-lung ventilation and pulmonary resection is variable according to first, the extent of impairment of pulmonary functions with associated alteration in pulmonary vessels decreasing the expand ability of the pulmonary vascular bed, and second, to the extent of surgery. Echocardiographic examination of right ventricular functions and pulmonary hemodynamics in the setting of pulmonary resection was restricted to pre-and post-operaterative periods. Intraoperative hemodynamic monitoring using TEE was suggested recently for both cardiac and non-cardiac surgery. Doppler-derived methods for assessment of PVR and right ventricular functions were recently introduced. Thirty patients were studied with mild to moderate impairment of pulmonary functions and normal both pulmonary pressure and cardiac functions. Assessment of intraoperative pulmonary hemodynamics and right ventricular functions was done using transesophageal echocardiography. Measurements were done at different stages of the procedure: at two lung ventilation, after thoracotomy and starting one-lung ventilation, after resection and lastly after resuming two-lung ventilation, for estimation of SPAP the peak velocity of TR recording by CWD of the tricuspid valve was used, this was applicable in 18 patients, in the other 12 patients we estimated MPAP from systolic intervals of pulmonary artery flow curve. A recently introduced method for assessment of PVR was used depending on systolic intervals of pulmonary artery curve. A recent method for assessment of overall functions of the right ventricle was used, the method dose not depend on geometric change in right ventricle during the cardiac cycle, instead it depends on time intervals derived from Doppler study of both trans-tricuspid flow and pulmonary artery systolic flow. The right ventricular fractional area of change (FAC) and CO were measured using the pulmonary artery velocity profile and the pulmonary artery diameter. Results showed a mild but statistically significant increase in pulmonary pressure with the onset of thoracotomy and starting one-lung ventilation, there was associated increase in CO but no significant change in PVR suggesting that the increase in pulmonary pressure was due to the increased CO, a possible mechanism for this increase could be the decreased intrathoracic pressure after thoracotomy with consequent increase inventricular filling. Further mild increase in pulmonary pressure was noticed following resection with associated significant increase in PVR. TEI index and RVFAC showed no change all through the procedure, all pulmonary hemodynamic data returned to near normal values at the end of surgery. It was concluded that one-lung ventilation and lobectomy in patients with mild to moderate impairment of lung functions produce mild but statistically significant changes in pulmonary pressure that returns back to normal at the end of surgery. We used two Doppler-derived methods that were recently introduced for assessment of both PVR and overall right ventricular functions, both methods appeared to be easily obtainable and reproducible, TEE appears to be a helpful guide in hemodynamic monitoring and can be informative for patient at risk of hemodynamic instability in non-cardiac surgery (category II indication in ASA/SCA guidelines).