Objectives:The prevalence of idiopathic normal pressure hydrocephalus (iNPH) and vascular comorbidity increases with age. It has not been clarified if high age and vascular disease are negative predictors of shunt surgery outcome in patients with iNPH.The aim of this study was to investigate the impact of high age and vascular comorbidity on outcome after shunt surgery in patients with iNPH.Methods: All 332 patients with iNPH who were treated with shunts between 2011 and 2015 at a single centre were consecutively included. Hellström iNPH scale, without the neuropsychological tests, was calculated preoperatively and at follow-up 12 months after shunt surgery. Outcome was defined as the difference between the post-operative and preoperative iNPH scale scores. A multivariable model was used to investigate the predictive effects of age and vascular comorbidity on shunt surgery outcome. Results:In a multivariable analysis of covariance (ANCOVA) with post-operative outcome as the dependent variable, increasing age (years, B = −0.63, P < .001) and history of ischaemic stroke (B = −10.06, P = .0038) were negative predictors of shunt surgery outcome after controlling for waiting time for surgery, symptom severity at preoperative control, presence of diabetes mellitus, hypertension, hyperlipidaemia, history of myocardial infarction, duration of symptoms and shunt complications. Conclusions:High age and established cerebrovascular disease are associated with less favourable outcome after shunt surgery in patients with iNPH.