Introduction: The HIV virus affects lymphocyte cells. Patients with HIV continue to suffer from cognitive and brain deficits, after antiretroviral treatment (ART). Substance abuse is making a complex and exacerbates the situation, despite treatment such as Methadone Maintenance Treatment (MMT). Brain imaging including resting-state fMRI (rs-fMRI) and Volumetric Brain Morphometry (VBM) have shown problems in both brain structures and connectivities among this population. We aimed our study to replicate previous studies by putting both rs-fMRI and VBM methods together. Method: A series of structural and functional images (5 minute resting state) were acquired from 12 individuals, 6 HIV-infected addicts under ART and MMT and 6 non-clinical ones, using Siemens 1.5 tesla MR scanner. All images were preprocessed (i.e., spatial normalization with modulation, segmentation, and smoothing) using SPM12 and relevant toolboxes under Matlab. The structural MRI images (axial, T1-weighted) were analyzed using VBM. The BOLD images were analyzed for functional connectivities. Results: Analyzing ROI-to- ROI at second-level for HIV-infected addicts compared to Control group and vice versa revealed decreases in functional connectivity especially from seed in right prefrontal to posterior cortical areas (applying p < 0.001, corrected). Also, lower connectivity (spatial component with seed-to-voxel maps) was found, all over the brain, especially in default mode network. Moreover, the result of VBM analysis at second-level (t-test) on gray matter (p < 0.001, corrected) revealed a decreased volume in HIV-infected addicts compared to Control all over the brain. Conclusion: The resting state fMRI (as well as VBM) results on brain images of HIV-infected addicts revealed decreases in structural (brain volume) and functional connectivity especially between prefrontal and posterior cortical. This finding is especially in line with the results from previous studies indicating network-level deficit
