Thermal　expansion　anomaly　studies　on　Nd(Fe,Mo)(12)N-x　(x=0,0.5,1)　compounds　were　performed　by　means　of　x-ray　and　neutron　diffractions.　Before　nitrogenation,　only　lattice　parameter　a　shows　abnormal　thermal　expansion　below　T-C.　In　Nd(Fe,Mo)(12)N-0.5,　both　parameters　a　and　c　show　abnormal　thermal　expansion　below　T-C,　while　only　c　shows　abnormal　thermal　expansion　in　the　Nd(Fe,Mo)(12)N　compound.　This　shows　that,　with　the　increase　in　the　N　content,　the　anomaly　gradually　changes　from　in　the　ab　plane　to　along　the　c　axis.　By　analyzing　the　Neel　curve　and　the　system　energy,　the　anomaly　was　mainly　attributed　to　the　contribution　of　some　strongly　positive　interactions,　which　is　quite　different　from　the　previous　explanation　for　thermal　expansion　anomalies.