Nitrogen (N) availability in forest soil is spatially heterogeneous, with large variability even at the centimeter-scale. However, most conventional methods cannot systematically reveal this heterogeneity with reasonable resolution under field conditions. To describe the distribution of soil N with high spatial resolution, we applied a novel technique, microdialysis. With microdialysis, the soil is sampled by inserting a small (0.5 mm in diameter) semi-permeable membrane. Soil solutes move through the membrane via induced diffusion when ultra-pure water is perfused behind the membrane. This enables sampling with minimal disturbance of the soil structure, particularly important for investigating the distribution of soil N compounds with small spatial intervals. The presented study was conducted at a fertilized site and a control site in a Scots pine forest in Northern Sweden. We collected microdialysis samples with small spatial intervals (minimal distance = 2 cm) within 1-square m plots, and soil samples (32 cm intervals). Nitrate, ammonium and amino acid diffusive flux rates were determined and their spatial distribution was analyzed with geostatistical methods. The same N compounds were determined for soil samples, and compared with microdialysis samples. Based on these results, we will discuss the spatial scale of soil N heterogeneity.