Scots pine (Pinus sylvestris) seedlots of different genetic quality were compared in realised gain trials at six sites in southern Finland at an age of 14–15 years. Synthetic seedlot mixtures of 1.5-generation plus trees showed consistent superiority to both first-generation orchard seedlots and unimproved checklots in growth, slenderness and relative branch size. Open-pollinated offspring from first-generation orchards, in turn, outperformed unimproved trees in most growth and quality traits. The mean incidence of ramicorns and forks was similar between unimproved and first-generation orchard trees, but slightly elevated in the 1.5-generation stock. Stand-level yields were projected for two virtual sites in southern Finland using simulation software MOTTI. The development of improved stands was modelled by incorporating genetic gains in height and diameter growth in the asymptote parameter of the Chapman–Richards growth function. The mean annual yields of the first-generation and 1.5-generation orchard stock were, as an average over the two sites, 11.5 and 23.9 % above the unimproved stock, respectively. For juvenile, fully contaminated 1.5-generation orchards, the genetic gain was 15.9 %. The predicted reduction in the length of commercial rotation due to genetic improvement varied between 4 and 17 years depending on the site, orchard generation, level of pollen contamination and genetic thinning. The results indicated substantial returns on investments on improved reforestation stock in southern Finland. Increments in bare land value (using a 3 % interest rate) ranged from 529 to 1836 € ha−1 (30.5–60.5 % above unimproved stock).