The rules of cyclization: Alkynylamides are regioselectively cycloisomerized into piperazin‐2‐one and 1,4‐diazepan‐2‐one derivatives by using catalytic amounts of appropriate metal catalysts. A 6‐exo‐dig addition proceeds in the presence of Bi(OTf)3, while the 7‐endo‐dig addition occurs with PtCl2 for the same substrate. (see scheme; Ns=o‐nitrobenzenesulfonyl, Ts=p‐toluenesulfonyl, Cbz=benzyloxycarbonyl