As a portable media device that enables ubiquitous access to friends and entertainment, smartphones are inextricably linked with our lives. Although there is growing concern about the detrimental effect of problematic smartphone use on attentional control, the underlying neural mechanisms of impaired attentional control in problematic smartphone users (PSU) has yet to be investigated. Using a modified cognitive conflict task, we examined behavioral performance in the presence of distracting words during functional magnetic resonance imaging in 33 PSU and 33 control participants (CON). Compared with the CON group, the PSU group demonstrated impaired performance that was accompanied by constantly enhanced but not differentiated activation in the frontoparietal regions across all conditions, regardless of distractor saliency. The inferior parietal lobule (IPL) activation in the PSU group, in particular, showed an association with performance deficits in the distractor conditions. Furthermore, the PSU group exhibited decreased functional connectivity of the right IPL with the right superior temporal gyrus of the ventral attention system in the attention-demanding condition relative to the easiest condition, which was associated with the severe dependence on smartphone use. Our findings suggest that greater distractibility in the PSU group during the attentional control task may be associated with inefficient recruitment of the ventral attention network involved in bottom-up attentional processing, as indicated by hyperactivation but less coherence within the network. The present study provides evidence for understanding the neural mechanisms underlying the impaired ability to keep attention from being oriented to task-irrelevant stimuli observed in PSU.