Glycaemic response to dietary carbohydrates might have an impact on cognitive performance. The present study investigated the effects of growing-up milks (GUM) with isomaltulose and extra minerals and vitamins or lower protein content on cognitive parameters in children aged 5–6 years. In a blinded, partly randomised, controlled, cross-over study, four GUM were provided, each taken over 14 d (2 × 200 ml/d): standard (Std) GUM; Std GUM+5 g isomaltulose (Iso-5 GUM); Iso-5 GUM with 26 % less protein (Iso-5 LP GUM); Std GUM with 2·5 g isomaltulose and extra Mg, Zn, Se, D3, B1, B2, B12, folic acid and choline (Iso-2·5 GUM). At test days, when GUM replaced breakfast, repeated (0, 60, 120 and 180 min post-dose) cognitive tasks were performed (picture presentation, simple reaction time, digit vigilance, choice reaction time, spatial and numeric working memory and picture recognition). Task performance of all subjects (n 50) worsened over the morning. Best performance was seen on isomaltulose GUM, most notably at 180 min. Iso-2·5 GUM showed best performance on several parameters of attention and memory, Iso-5 GUM performed best on parameters of memory and Iso-5 LP GUM was positively associated with parameters of attention but less with memory. Std GUM showed only a benefit on one attention and one memory task. Thus, isomaltulose-enriched GUM positively affected parameters of attention and memory at 180 min post-dose when compared with Std GUM. Extra minerals and vitamins seem beneficial, whereas lowering protein content might improve attention in particular.