The importance of the posterior cerebral artery (PCA) involvement in moyamoya disease has been highlighted in recent years. However, few studies compared the impact of PCA lesions in moyamoya disease between pediatric and adult patients. We conducted this study to summarize the clinical features of moyamoya patients with PCA lesions and describe the difference between pediatric and adult patients. We reviewed the records of 696 consecutive moyamoya vasculopathy patients from 2009 to 2015. The Suzuki and the Miyamoto stages were used to evaluate the stenoocclusive lesions of the anterior and posterior arteries. Clinical and radiographic features were compared between those with and without PCA involvement, also between pediatric and adult patients. A total of 574 angiograms (140 pediatrics and 434 adults) were reviewed. The prevalence of PCA steno-occlusion did not differ significantly between pediatric patients and adult patients (35.0% vs. 30.4%, P = 0.347). Pediatric patients had more advanced PCA stages compared to adult patients (P = 0.045). There was a significant correlation of the PCA angiographic stages with the ipsilateral internal carotid artery (ICA) stages, both in pediatrics and in adults (both P < 0.001). The frequency of ipsilateral cerebral infarction positively correlated with the advancement of PCA stages in adult patients (P < 0.001), but not significant in pediatric patients (P = 0.106). Pediatric patients tend to have more advanced PCA lesions than adult patients. The degree of PCA steno-occlusion positively correlates with the ipsilateral ICA stage, both in pediatrics and in adults.