This study presents the tectonic analysis of deformation structures in Slemmestad area. The study area lies in the southwest of Oslo. The analysis is conducted to better understand the fracture development and deformation in the folds of fold and thrust belt, in basement and in Permian. The outcrop data is collected by using a scanline technique. This outcrop study has been carried out to collect different fracture parameters. A systematic relationship is observed between the fracture sets and fold geometry in the Paleozoic succession. The mechanism in the fold development is likely flexural slip folding and orthogonal flexural folding. The maximum tectonic stress in the study area is NW-SE, which links and explains the dominant NW-SE open fracture sets in the folds of Cambro-Silurian succession. The fracture intensity is controlled by the structural position of the folds. In more detail, the hinge zone and the areas where the folds are plunging offer the highest fracture intensities. The fracture sets can be explained by different stages of developments; 1) Foreland fractures formation of NW-SE. 2) The fold related stage of NE-SW oriented fractures which are possibly formed due to outer arc extension. 3) N-S trending fractures either formed or reactivated during the development of Oslo rift. The fractures in the basement are WNW-ESE and NNW-SSE trending and do not show any relationship with Cambro-Silurian succession and therefore, formed prior to the Caledonian Orogeny. The fractures in the Cambro-Silurian succession and Permian sill intrusion show similar trend which could suggest the reactivation of previously formed fractures.