Inflamed human periodontal and peri-implant (ITI Bonefit) gingival tissues were studied immunohistochemically to evaluate the possible presence of structural differences in the extracellular matrix protein localization. Collagen types I, III, IV, V, VI, and VII and fibronectin showed a similar distribution in these tissues. Data show that morphologic structural differences between these inflamed tissues are not present. According to these findings, the connective tissue response of inflamed peri-implant as well as periodontal gingival tissues should be similar during treatment when the inflammation is localized only in the soft tissue level. Keywords: collagen, extracellular matrix, fibronectin, gingiva, inflammation, peri-implant soft tissues