This paper discusses the results of a study on the impact of nitrogen stress on the accumulation of various N forms in young pines and in needles of mature pine trees. With the increase in N content in the growth environment (fertilization), a several fold increase in total N in plants was found while N-NH4 increased tens of times as compared to the treatment without fertilization. At a decreased biomass yield by ca. 50 % the proportion of N-NH4 in the total N pool fluctuated from IO to 15 %, or even more. The share of N-NO3 in the total N amount was several fold lower than that of N-NH4. In needles of trees growing under the impact of N deposition, the observed share of N-NH4 in the total N pool was at a level of ca. 3 %. but the total amount of soluble non-protein N compounds constituted ca. 26 %. In needles of trees under low N deposition only trace amounts of mineral N were detected. Thus it can be suggested that the ratio of total N to soluble non-protein N compounds as well as the total N to mineral N ratio may be used as indices of N stress for pine.