Summary: Signed difference sets have interesting applications in communications and coding theory. A \((v,k,\lambda )\)-difference set in a finite group \(G\) of order \(v\) is a subset \(D\) of \(G\) with \(k\) distinct elements such that the expressions \(xy^{-1}\) for all distinct two elements \(x,y\in D\), represent each non-identity element in \(G\) exactly \(\lambda\) times. A \((v,k,\lambda )\)-signed difference set is a generalization of a \((v,k,\lambda )\)-difference set \(D\), which satisfies all properties of \(D\), but has a sign for each element in \(D\). We will show some new existence results for signed difference sets by using partial difference sets, product methods, and cyclotomic classes.