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Beside that it is possible to use the sanitary waste as raw material, landfilling is still the most wide used technique in Serbia. Although that landfilling – according to the waste hierarchy – is treated as an unfavourable solution, it, however, enables systematic data collection, which can be commented as practice improvement, when compared to old dumps. Mechanical reconstitution of municipal solid waste by compaction represents one of the elementary methods for waste’s treatment. The influence of composition and age of municipal solid waste on the parameters achived by Proctor’s test (dry unit weight and optimal moisture content) will be commented in the paper. For that purpose, results for samples prepared from landfill in Plandište (cca 10 years old) and from Ada Huja landfill in Belgrade (about 40 years old) will be compared. Thus, by preparing artificial samples in laboratory conditions, the importance of this property will be presented for the purpose of optimization of landfill’s area. Moreover, the paper will give a criteria for determining the composition for preparing samples for two landfills with different age.