With the aim to gain a wider understanding on the design rules of bioinspired adhesives for application in the medical field, the adhesion of fibrillar structures on soft and stiff polymers was determined in bench top studies on surfaces with variable roughness and in ex-vivo wet tissue tests. The adhesion strength of stiff fibrillar structures was found to be dependent on the roughness of the adherent surface. For a given fibril width and density, the optimal adhesion was seen when the length of the fibrils was of the same range as that of the roughness of the surface it was tested against. Over this limit, the adherence decreased. In the case of soft adhesive structures, the same trend was observed where an optimum adhesion was seen when the size of the pillars matched that of the adherent surface roughness. This observation was attributed to an increase in surface contact. The adhesion of fibrillar structures on tissue samples in ex-vivo tests showed a similar trend with enhanced fibrillar interpenetration favoring a larger number of contacts and a stronger capillary force expected to account for the adhesion enhancement.