The measurement of daily physical activity (PA) has become a significant outcome in patients with chronic obstructive pulmonary disease (COPD). Recent data have shown the independent association between PA markers, hospitalizations, and mortality. Daily PA can be quantified by direct observation, assessment of energy expenditure, questionnaires, and activity monitors (motion sensors). This review aims to describe the methods used to quantify daily PA in COPD on the basis of the published literature and to suggest potential applications of activity monitoring methods in clinical research and daily care of COPD patients.