Thinning is one of the primordial silvicultural practices. It has been analysed by its methods and intensities, associated to the tree selection criteria. Yet, while some methods are of generalised use, others were developed for specific purposes. The goal of this review is to compile the existing information regarding tree selection, thinning methods and intensity as well as their effects on trees and stands. The effects of thinning indicate a reduction of density and a trend towards an increase of growth rates at tree level for a short time after thinning. Biomass and volume show similar or smaller values when compared to unthinned stands. Mortality and growth stagnation, especially in stands with low stability or vigour, can also occur. The modifications in stand structure can enhance its role as an adaptive measure.