Abstract: Objective To investigate the feasibility of magnetic resonance spectroscopy(MRS) in the diagnosis of benign and malignant pleural effusions. Methods Samples of 46 cases of pleural effusion were collected in clinics after performing pleurocentesis. Among the obtained samples, 20 cases were benign pleural effusion(14 cases of tuberculosis and 6 cases of pneumonia) and 26 cases were malignant pleural effusion(18 cases of primary bronchogenic carcinoma, 5 cases of breast carcinoma, 2 cases of primary hepatic carcinoma, and 1 case of gastric carcinoma). The effusion pleural samples were centrifuged and subjected to 1H MRS examination using a 1.5T MR device. Results The main metabolites in the pleural effusion contain lactate, choline, creatine, myo-inositol(MI), and fatty acids. Area of Lactate: pleural effusion from tuberculosis (5.19±1.31), pneumonia (6.08±1.56) and malignant pleural effusion (2.40±0.43) has statistic significance (F=8.45, P < 0.01). Area of choline: pleural effusion from tuberculosis (2.75±0.91), pneumonia (3.27±1.21) and malignant pleural effusion (6.76±1.73) has statistic significance (F=2.98, P < 0.01). Area of MI: pleural effusion from tuberculosis (2.71±1.19), pneumonia (2.25±0.81) and malignant pleural effusion (5.83±2.08) has statistic significance (F=38.49, P < 0.01). Area of lactate(t=-1.04, P > 0.05), choline(t=-0.58, P > 0.05) and MI(t=1.19, P > 0.05) between pleural effusion from tuberculosis(5.19±1.31) and pneumonia has no statistic significance. Conclusions Benign and malignant pleural effusions show different MRS characteristics. 1H MRS has certain clinical value in the differentiation of benign and malignant pleural effusions.