N-nitrosamines exist as two zowitter ions which are more stable than their neutral form. In the case of symmetric cyclo N-nitrosamines with two nitroso groups, various studies were done on products which derived from piperazine. In order to nitrosation of only one of the NH groups the reaction was proceeded with 1mmol of NaNO2. It is observed that nitrosation on the both of the NH groups are done, unexpectedly and half of the piperazine are remained intact. In the presence of 2 mmol of NaNO2 per 1mmol piperazine, the whole of piperazine convert to N,N-dinitrosopiperazine which exist in two cis- and trans- chair conformations. In the presence of 4 mmol of NaNO2 per 1mmol piperazine, the whole of piperazine convert to N,N-dinitrosopiperazine which exist in four conformers of cis- and trans- forms of chair and boat conformations.