The impact of undergrowth and its pre-clearance methods on the productivity, costs, and silvicultural result of the winter and summer harvesting of first-thinning Scots pine (Pinus sylvestris) stands, and as well as the profitability of pre-clearance were analysed. The density and average height of the Norway spruce (Picea abies) undergrowth were found to have a significant impact on cutting productivity. Spruce undergrowth density also affected forwarding productivity. Undergrowth density, height, or pre-clearance method had no effect on the silvicultural result. The density and average height of the spruce undergrowth, the size of the trees to be harvested, the roundwood removal, and the costs for harvesting machinery used affected the calculated pre-clearance limits. The pre-clearance limit refers to the spruce undergrowth level, above which pre-clearance became economically profitable. Based on the findings of this study, when the spruce undergrowth density in a marked pine stand exceeds the pre-clearance limit, the most effective pre-clearance result is achieved when a one-metre radius is cleared around each merchantable stem together with any other spruce undergrowth over 1.5–2.0 m high that may hinder cutting.