Liming was and still is carried out in many European forests since the beginning of the 1980s. Main objectives of compensation liming is to neutralize actual acidic deposition in order to prevent further soil acidification, to increase base saturation and acid buffering capacity of the soil. This paper evaluates results from long-term liming experiments throughout Europe using different amounts and forms of liming materials. Differences in forest ecosystem reaction to liming can be caused by amount, form and frequency of the application, and by the solubility, reaction kinetics, contents and composition of the material used. Furthermore, other factors like climate, site history, management, environmental conditions (e.g. actual and historical deposition rates), humus form, C/N ratio, nitrogen stores, and the soil chemical properties (e.g. pH, base saturation, CEC) may strongly influence the effects of liming treatments. Element budgets of forested ecosystems on a plot or watershed scale provide a very useful tool to integrate the various effects of additional Mg inputs via liming/fertilization.