PURPOSE: An estimated 50 million people in the Europe live with multi-morbidity (MM). Research has found that those with MM have a greater risk of physical function (PF) decline and poorer quality of life (QoL) than those with a single chronic disease (SCD). The aim of this study was to compare the physical activity (PA) levels and sedentary behavior (SB) in patients with MM and SCD and to investigate the association between PA and PF and QoL. METHODS: Subjects (n=229, 54.4% female, age (mean±SD) 62.2±11.1 yr) were recruited at induction to a community-based exercise program for chronic disease. Medical history was obtained from a referral letter provided by a healthcare professional. Subjects with a single diagnosis of a chronic disease, primarily including cardiovascular, respiratory disease, cancer, diabetes, were classified as SCD. Participants with ≥2 of these diagnoses were classified as MM. BMI and waist to hip ratio (WHR) were measured and calculated using standard procedures. Upper and lower body strength, flexibility and cardiorespiratory fitness were assessed using a hand-grip test, sit-to-stand test (STS), sit and reach test (SRT), and 6-min time trial (6MTT), respectively. PA and SB were recorded using an activPAL3 micro accelerometer. QoL was assessed using the EQ5D VAS. Independent sample T tests were used to compare MCD with SCD on measures of PA, SB, PF and QoL. General linear models were used to investigate the association between PA and SB and PF and QoL RESULTS: 102 (44.5%) participants were defined as MM. Participants with MM had higher waking SB (9.3 ± 1.8 vs 9.9 ± 1.9 hrs/d, p=.013),lower MVPA (0.3 ± 0.2 vs 0.4 ± 0.2 hrs/d, p=.001) and daily step count (6185 ± 3016 vs 7270 ± 3196 steps/d, p=.009) compared with SCD. MM had higher BMI (31.6 ± 7.3 vs 28.0 ± 5.3 kg/m2), (p=.000 for all). MM achieved significantly poorer results for the STS (23.8 ± 9.6 vs 21.2 ± 7.3 s, p=0.21) and 6MTT (453.3 ± 118.9 vs 514.4 ± 113.2 m, p=0.00). There were no differences between groups for WHR, SRT and QoL. MVPA was significantly related to weight, BMI, 6MTT,daily step count was related to STS, 6MTT and QoL and waking SB was related to WHR. CONCLUSIONS: Individuals with MM had greater SB and less PA than those with SCD. PF was poorer for individuals with MM. There were significant associations between PA with physical function and QoL in a CD population.