Summary: Let \(R\) be a commutative ring with identity \(1\ne 0\). Define the comaximal graph of \(R\), denoted by \(CG(R)\), to be the graph whose vertices are the elements of \(R\), where two distinct vertices \(a\) and \(b\) are adjacent if and only if \(Ra+ Rb= R\). A vertex \(a\) in a simple graph \(G\) is said to be a Smarandache vertex (or S-vertex for short) provided that there exist \(x\), \(y\), and \(b\) (all different from \(a\)) in \(G\) such that \(a- x\), \(a-b\), and \(b-y\) are edges in \(G\) but there is no edge between \(x\) and \(y\).
The main object of this paper is to study the S-vertices of \(CG(R)\) an \(CG_2(R)\setminus J(R)\) (or \(CG_J(R)\) for short), where \(CG_2(R)\) is the subgraph of \(CG(R)\) which consists of nonunit elements of \(R\) and \(J(R)\) is the Jacobson radical of \(R\). There is also a discussion on a relationship between the diameter and S-vertices of \(CG_J(R)\).