Historically, attention-deficit hyperactivity disorder (ADHD) was conceptualised as a disorder of childhood that gradually improved and diminished as individuals transitioned to adulthood. Over the past decade, several studies have been published describing a cohort of adolescents with a childhood diagnosis of ADHD experiencing a continuity of ADHD symptoms into adulthood. Untreated ADHD in adults is associated with personal relationship difficulties, educational and occupational underachievement, comorbid mental health problems, substance misuse, and increased rates of road traffic accidents and criminality. These result in an increased economic burden and broader public health challenges. This review outlines the current framework and stage of development of ADHD services for adults in the Republic of Ireland.