Aims Improved behaviour, mood, cognition and HbA1c have been reported with short-term use of continuous subcutaneous insulin infusion (CSII) in youth with type 1 diabetes (T1D). We sought to re-examine these findings in a randomised controlled trial (RCT), with longitudinal follow-up. Methods RCT of youth aged 7-15 years with T1D, at two tertiary paediatric centres. Participants were randomised to commence CSII or continue multiple daily injections (MDI). Behaviour, mood, cognition and HbA1c were assessed. Primary outcome was difference in parent-reported behaviour (BASC-2) at 4 months. After the 4-month RCT, MDI participants commenced CSII; outcomes were reassessed at +2 years. Results Participating youth (n=101) were randomised to CSII (n=56) or MDI (n=45). Significant differences favouring CSII were found at 4 months in parent-reported behaviour problems (Cohen’s d 0.41 (95% CI 0.004 to 0.795); p=0.048) and HbA1c (mean (95% CI) difference: 7 (2.3 to 11.7) mmol/mol (0.6% (0.2 to 1.0%); p=0.001)). Improvements from baseline were documented in mood and cognitive outcomes in both study groups over the 4-month RCT; however, no between-group differences were evident at 4 months. Sixteen of 76 (21%) participants completing assessments at +2 years had discontinued CSII. In n=60 still using CSII, measurements of behaviour, mood and HbA1c were comparable to baseline. Conclusions Parent-reported behaviour problems and HbA1c, but not mood or neurocognitive outcomes, were clinically significantly lower with CSII, relative to MDI, after 4 months. Observational follow-up indicated no impact of treatment modality at +2 years, relative to baseline levels. Taken together, these data indicate that use of CSII alone does not comprehensively benefit neuropsychological outcomes in childhood T1D.