Abstract Extracellular matrix (ECM) in nasal polyps is characterized by a subepithelial infiltration of eosinophils and pseudocyst formations. The processes leading to the vacuolisation of the ECM remain unclear but the role of matrix metalloproteinases, because of their proteolytic activities against the different components of the ECM, has been evoked. Immunohistochemistry for MMP-7, MMP-9 and TIMP-1 was performed on frozen sections from 10 controls, 10 patients with nasal polyposis (NP) and 10 with chronic sinusitis (CS). ELISA measurements were performed on tissue homogenates. In NP, when compared to CS or control samples, a staining for MMP-9 and MMP-7 appeared in blood vessels. In NP, MMP-9 was also upregulated in epithelium in glands and MMP-9-positive mononuclear inflammatory cells were increased, especially in the centre of pseudocyst formations. Concentrations of MMP-9 protein were found significantly increased in both CS and NP compared to controls, while MMP-7 was significantly increased in NP compared to controls and CS. TIMP-1 protein was significantly increased in CS, but not in polyps, when compared to normal mucosa. CS and NP show different patterns of MMP-7/-9 and TIMP-1 expression. This difference in regulation of enzymatic proteins could form the basis for the different tissue remodelling processes of these sinus diseases.