Although the presence of pulmonary lymphoid follicles (LFs) has been associated with the progression of chronic obstructive pulmonary disease (COPD), there is no information regarding the pattern of vascularisation, expression of addressins or inflammatory cell densities within these structures in COPD. Histological and immunohistochemical techniques were used to assess the prevalence, structure, localisation, vascularisation and cell proliferation/apoptosis of LFs, as well as the follicular density of B- and T-lymphocytes, macrophages, dendritic cells and CD57(+) cells, in lung tissue of nine nonsmokers, 18 smokers without COPD, 16 smokers with moderate COPD and 16 patients with very severe COPD. The density of CD57(+) cells within LFs of COPD patients was significantly increased compared to that of nonsmokers and smokers without COPD (p<0.05). Moreover, the percentage of LF profiles with cell apoptosis was also significantly higher in COPD patients (p = 0.03). By contrast, no significant differences among groups were observed in the follicular densities of other inflammatory cells, nor in the distribution of blood and lymphatic vessels within LFs. Since CD57(+) cells are important effectors of cytotoxicity and immune regulation, an increase in their follicular density supports the hypothesis of local immune dysfunction in COPD.