  We consider the ring $\mathbb Z_n$ (integers modulo $n$) with the partial
order `$\leq$' given by `$a \leq b$ if either $a=b$ or $a\equiv ab~(mod~n)$'.
In this paper, we obtain necessary and sufficient conditions for the poset
($\mathbb Z_n,~\leq$) to be a lattice.
