Increasing numbers of students in UK universities are presenting with a diagnosis of attention deficit hyperactivity disorder (ADHD). However, the impact of ADHD symptomatology on academic achievement in university students in the UK has not previously been explored. This study investigates the prevalence of self-reported ADHD symptoms (inattention, hyperactivity and impulsivity) in 464 undergraduate psychology students across two year cohorts. Findings suggest that there is a high incidence of undiagnosed students in the at risk categories for ADHD. Students who score higher on the inattention subscale are more likely to achieve a lower final average percentage mark (APM) and are significantly less likely to complete their degree within three years. The study suggests a need to focus on the identification and provision of support for students with elevated ADHD symptomatology, particularly inattention characteristics, irrespective of a previous diagnosis of ADHD.