The functional connectivity (FC) of striatal subregions is correlated with cognitive functions in child attention deficit hyperactivity disorder (ADHD). However, increasing age changes the pattern of cognitive functions and clinical presentation. The changes in the pattern of cognitive functions may be associated with underlying age‑dependent striatal subregional FC alterations. We attempted to explore aberrancies in FC in striatal subregions and their associations with a predominant cognitive symptom (inattention) in adult ADHD. The FCs of ten bilateral subregions (seeds) of the striatum along with the whole brain were investigated, and FC maps of adults with ADHD (N=15) and healthy controls (N=15) were compared. Finally, we evaluated the associations of striatal subregional FCs with cognitive functions. Case‑control differences in striatal subregional FC were not significant; however, attention scores were marginally significantly positively correlated with FC between the right dorsal‑caudal putamen and right‑superior temporal gyrus in the ADHD group. Our results suggested that cognitive deficits (inattention) may be associated with FC aberrancy in a substriatal connection (between the right dorsal‑caudal putamen and right‑superior temporal gyrus) in adult ADHD.