Abstract: Objective To evaluate the application of the maximum standardized uptake value (SUV_max) from PET/CT and apparent diffusion coefficient(ADC) from multi b-values DWI in differentiating benign from malignant lung diseases using a trimodality PET/CT-MRI and analyze the molecular correlation between SUV_max and ADC. Methods A retrospective study was performed in 33 consecutive patients who were pathologically or clinically diagnosed with pulmonary lesions. All patients underwent ¹⁸F-FDG PET/CT before MRI examination, obtaining the SUV_max of pulmonary lesions and the ADCs of multi b-values DWI, including ADC-fast related to micro-perfusion obtained low b-value DWI, ADC-slow related to pure diffusion from middle b-value DWI and ADC- aquaporin (AQP) related to AQP from high b-value DWI. The differences in SUV_max and ADCs between benign and malignant pulmonary lesions were analyzed by independent-sample t test. The ROC curve was plotted to evaluate the diagnostic efficiency of SUV_max and ADC. The correlation between SUV_max and ADC in each multi-b value DWI section was evaluated by Pearson correlation analysis. Results The SUV_max of pulmonary malignant lesions was significantly higher than that of benign lesions (t=-3.105,P=0.004). The ADC-slow of pulmonary malignant lesions was significantly lower than that of benign lesions (t=2.688,P=0.011).The cut-off value of SUV_max in differentiating benign from malignant lung diseases was 4.95 g/ml, with a sensitivity of 95.8% and a specificity of 77.8%. The cut-off value of ADC-slow in differentiating benign from malignant lung diseases was 0.15×10^-3mm²/s, with a sensitivity of 77.8% and a specificity of 66.7%.No significant correlation was found between SUV_max and ADC in each multi-b value DWI section. Conclusions SUV_max and ADC-slow are helpful to differentiate benign from malignant lung diseases. There is no significant correlation between SUV_max and ADCs, which indicate different biological information.