Aquaporins (AQPs) are a family of hydrophobic integral membrane proteins that function as transmem- brane channels and play an important role in tissue homeostasis. Aquaporin-1 (AQP1), in particular, has been reported to be involved in several biological processes including inflammation, angiogenesis, wound healing and others. Periodontitis and peri-implantitis can be defined as inflammatory processes that affect the tissues surrounding a tooth or an osseointegrated implant, respectively. To date, there are limited data about the involvement of AQPs in these diseases. The aim of this study was to evalu- ate the possible link between the histomorphological alterations and the expression of AQP1 in healthy, pathological and healed periodontal and peri-implant gingival tissues. The results obtained showed that changes in organization of collagen fibers were observed in periodontitis and peri-implantitis, together with an increase in the percentage of area occupied by inflammatory cell infiltration and an increase of AQP1 immunostaining, which was located in the endothelial cells of the vessels within the lamina propria. Moreover, in healed periodontal and peri-implant mucosa a restoration of histomorphological alterations was observed together with a concomitant decrease of AQP1 immunostaining. These data suggested a possible link between the degree of inflammatory state and the presence of AQP1, where the latter could be involved in the chain of inflammatory reactions triggered at periodontal and peri-implant levels.