<p>Forests in Europe have acted as an important carbon sink since the mid-20th century. However, in recent years, signs of sink saturation have emerged due to a decline in carbon uptake. As a result, land managers have to explore strategies to enhance the long-term climate mitigation potential. We aimed to assess the potential contribution of different long-term forest management scenarios in Latvia. We evaluated the climate change mitigation effect of managed stands using wood-based substitution and compared them with old-growth stands, which represent the potential maximum carbon storage. We assessed 84 old-growth (average age 151 years) and younger 266 managed stands (average age 76 years) growing on mineral soil. Our results show that carbon stock in tree biomass for all analyzed tree species was on average 20% higher in old-growth stands than in managed stands. The climate mitigation effect in managed stands was assessed in three scenarios, considering the tree biomass carbon stock and carbon storage in harvested wood products together with substitution effect. The total climate change mitigation effect achieved in all modeled scenarios for managed stands was significantly higher (by 41–66%, when substitution rate for recycled textile instead of fuelwood was applied) compared to carbon stock in tree biomass of old-growth stands. Our estimates for managed forests are likely conservative, as we considered carbon storage in wood products from final felling. These results suggest that the long-term climate mitigation effect of old-growth stands is significantly smaller than the total effect achieved in managed stands over a similar period and could be substantially enhanced through the use of wood products with a higher substitution effect.</p>