Purpose: To assess any correlation of volume transfer constant (K trans) with apparent diffusion coefficient (ADC) in different brain tumor types at 3 T magnetic resonance (MR) imaging. Materials and methods: Thirteen patients with brain tumors (8 men, 5 women; mean age 54.6 ± 17.7 years) were enrolled in this retrospective study. All patients underwent dynamic contrast-enhanced T 1-weighted MR perfusion and diffusion-weighted imaging using a 3 T scanner. K trans was estimated by specially designed software. For each tumor, regions of interest (ROIs) were manually selected on corresponding K trans and ADC maps. Pearson correlation coefficients were obtained for maximum, mean and minimum values of K trans and ADC of all ROIs. Based on clinicopathologic results, the final diagnoses of patients were glioblastoma multiforme (3), low-grade to anaplastic gliomas (4), meningiomas (3) and metastatic tumors (3). Results: K trans(max) values were significantly inversely correlated with ADC(min) values (r=-0.536, Ptrans(mean) and K trans(min) values were significantly inversely correlated with ADC(mean) (r=-0.228, P=0.038) and ADC(max) values (r=-0.355, P=0.001), respectively. Conclusion: We found that irrespective of brain tumor type, there is an inverse correlation between ADC and K trans. Our findings highlight an intricate relationship between vascular permeability and the tumor microenvironment, probably modulating and/or interacting with changes such as increased cellularity, ischemic insult and varying extracellular matrix composition. © 2012 International Cancer Imaging Society.