The plasma polymerization of allylamine was often investigated to modify polymer surfaces with primary amino groups. However, this deposition process is characterized by a significant loss of NH2 groups originally present in allylamine. To compensate this loss of NH2 groups in the deposited plasma polymer layer ammonia was added to the plasma process. Indeed, huge amount of nitrogen could be incorporated into the plasma polymer using addition of ammonia but the yield in primary amino groups was not increased. Extensive side-reactions were observed. Such NH2 group-enriched polymer surfaces are interesting for bio-applications. The influence of NH3 addition to allylamine on the yield of primary amino groups was characterized using FTIR-ATR, X-ray photoelectron spectroscopy and differential scanning calorimetry.