Purpose <p>This study investigated the quality of life in adults with diagnosed or suspected ADHD in New Zealand, comparing suspected ADHD (self-reported symptoms without formal diagnosis) and those formally diagnosed (medicated/unmedicated).</p> Methods <p>New Zealand residents aged 18 + with diagnosed or suspected ADHD (<i>N</i> = 329) responded to an online Qualtrics survey including: demographic questions; ASRS-5-RS Scale (proprietary scoring); and Adult ADHD Quality of Life Scale (AAQoL). Statistical analyses included Spearman correlations, while group comparisons were conducted using Mann-Whitney U and Kruskal-Wallis tests.</p> Results <p>A moderate negative correlation exists between increased ADHD symptom severity and lower quality of life (<i>p</i> &lt; .001). The Diagnosed Group (<i>n</i> = 232) were higher in median age than the Suspected Group (<i>n</i> = 97) (<i>p =</i> .018). No significant differences in ASRS-5-RS scores were observed between groups (<i>p =</i> .573). The Suspected Group reported significantly lower AAQoL scores than the Diagnosed Group (<i>p = &lt;</i> 0.001), which persisted when comparing the Suspected and Diagnosed subgroups with (<i>n</i> = 183) and without (<i>n</i> = 49) ADHD medication (<i>p</i> &lt; .001).</p> Conclusion <p>A high proportion of women and gender diverse individuals were represented, reflecting recent trends in adult ADHD diagnoses and support-seeking behaviour, expanding on previously underrepresented demographics. Across Suspected and Diagnosed groups, lower quality of life was associated with higher ADHD symptomology, regardless of medication status. Notably, the Suspected group reported significantly lower quality of life than the Diagnosed groups, particularly those on medication. Findings underscore the need for improved early, accessible diagnostic services and comprehensive support systems in addition to medication.</p>