lt;bgt;Objectivelt;/bgt; To investigate the association between multimorbidity and PreferenceWeighted Health Related Quality of Life (PWHRQoL), a score that combines physical and mental functioning, and how this varies by socioeconomic deprivation and age.lt;pgt;lt;/pgt; lt;bgt;Designlt;/bgt; The Scottish Health Survey (SHeS) is a cross-sectional representative survey of the general population which included the SF-12, a survey of HRQoL, for individuals 20 years and over.lt;pgt;lt;/pgt; lt;bgt;Methodslt;/bgt; For 7,054 participants we generated PWHRQoL scores by running SF-12 responses through the SF-6D algorithm. The resulting scores ranged from 0.29 (worst health) to 1 (perfect health). Using ordinary least squares, we first investigated associations between scores and increasing counts of longstanding conditions, and then repeated for multimorbidity (2+ conditions). Estimates were made for the general population and quintiles of socioeconomic deprivation. For multimorbidity, the analyses were repeated stratifying the population by age group (20--44, 45--64, 65+).lt;pgt;lt;/pgt; lt;bgt;Resultslt;/bgt; 45% of participants reported a longstanding condition and 18% reported multimorbidity. The presence of 1, 2, or 3+ longstanding conditions were associated with average reductions in PWHRQoL scores of 0.081, 0.151 and 0.212 respectively. Reduction in scores associated with multimorbidity was 33% greater in the most deprived quintile compared to the least deprived quintile, with the biggest difference (80 in the 20--44 age groups. There were no significant gender differences.lt;pgt;lt;/pgt; lt;bgt;Conclusionslt;/bgt; PWHRQoL decreases markedly with multimorbidity, and is exacerbated by higher deprivation and younger age. There is a need to prioritise interventions to improve the HRQoL for (especially younger) adults with multimorbidity in deprived areas.