Knowledge on the effects of DBS on cognitive functions is limited and no data exists on the effects of constant-current DBS (CC-GPi-DBS), which appears to prevail over constant-voltage stimulation. Our aim was to prospectively assess the effect of Constant-Current-GPi-DBS, using an 8-contact lead, on cognition, mood and quality of life.Ten patients aged 27-49 underwent prospective neuropsychological assessment using dedicated tests. Various cognitive domains (intelligence, executive functions, memory, attention, visuo-spatial perception, verbal intelligence) as well as emotional state and quality of life were examined preoperatively and 1, 6 and 12 months after continuous constant-current DBS.Patients performed preoperatively below average on information processing speed, phonemic verbal fluency and working memory. At 6-months there was an improvement in phonemic verbal fluency (p < .05), which was retained at 12-months postoperatively (p = .05). Results also showed marginal improvement in the Trail Making-A test (p = .051) and the Stroop colour-word test (p < .05). Despite improvement in Quality of Life (Physical and Mental Component improved by 32.42% and 29.46% respectively), patients showed no discernible change in anxiety and depression status.CC-GPi-DBS for primary dystonia has no discernible negative impact on cognition and mood. If anything, we noted an improvement of certain cognitive functions.