Earlier diagnosis of COPD is a major public health challenge as symptoms may be attributed to the normal consequences of aging. The optimum strategy for identifying patients with COPD remains to be determined. People aged 35 and over (n = 1896) on a GP practice register were randomised to either invitation or an opportunistic lung health check which included spirometry, quadriceps strength and MRC dyspnoea score. Then, 101 participants subsequently completed the General Practice Physical Activity Questionnaire. A total of 335 attended over a 15-week period; 156 were in the invitation group and 179 from the opportunist group. In 25 persons, spirometry was unsatisfactory or contraindicated. Spirometry was normal in 204(65.8%) and restrictive in 36(11.6%). 70(22.6%) had airflow obstruction, corresponding to Global Initiative for Chronic Lung Disease (GOLD) stages I-IV in 18(5.8%), 35(11.3%), 14(4.5%) and 3(1.0%), respectively. The opportunist group were significantly more likely to have airflow obstruction 30.1% vs 14.3% (p = 0.001). Breathlessness was reported commonly (40.5%) and quadriceps strength correlated significantly with MRC dyspnoea score independent of age, sex, pack-years smoked, fat-free mass and FEV(1) percent predicted. This relationship was also present in the subgroup of healthy participants (n = 143). 51.5% of participants screened were classified as "inactive" and this group were weaker and more breathless than those who were more active. Airflow obstruction was more common in those screened opportunistically. Breathlessness and inactivity are common in patients taking part in spirometry screening. Breathlessness is significantly associated with leg strength independent of spirometry and should be amenable to interventions to increase physical activity.