Reachability and observability Gramians are defined for the descriptor systems

and

. The pencils

and

are assumed to be regular. If

is singular,these Gramians do not, in general, satisfy the "expected" Lyapunov-like (Sylvester) equations (for example,

if

is the continuous-time teachability Gramian). This is shown by expressing the solution of the descriptor system in terms of the parameters of the Laurent expansion of

or

. We derive the Lyapunov-like equations which these Gramians do satisfy.