Free water (FW) index, a measure of extracellular non-flowing water in the brain parenchyma, can be sensitive to neuroinflammation. We examine the relationship between the FW index and putative markers of neuroinflammation in cART-naïve participants before and after 12 weeks of the treatment. We found that FW index correlated with neuroinflammation markers in HIV+ participants for some GM and WM structures at baseline while this correlation diminished after 12 weeks of cART treatment in some WM structures for NfL.