We investigate finite dimensional simple Lie algebras over an algebraically closed field F {\mathbf {F}} of characteristic p ⩾ 7 p \geqslant 7 having a Cartan subalgebra H H whose roots are dependent over F {\mathbf {F}} . We show that H H must be one-dimensional or for some root α \alpha relative to H H there is a 1 1 -section L ( α ) {L^{(\alpha )}} such that the core of L ( α ) {L^{(\alpha )}} is a simple Lie algebra of Cartan type H ( 2 : m _ : Φ ) ( 2 ) H{(2:\underline m :\Phi )^{(2)}} or W ( 1 : n _ ) W(1:\underline n ) for some n > 1 n > 1 . The results we obtain have applications to studying the local behavior of simple Lie algebras and to classifying simple Lie algebras which have a Cartan subalgebra of dimension less than p − 2 p - 2 .