  Unimodular Gravity is one of the oldest geometric gravity theory alternative
to General Relativity. Essentially, it is based on the Einstein-Hilbert
Lagrangian with an additional constraint on the determinant of the metric. It
can be explicitly shown that Unimodular Gravity can be recast as General
Relativity in presence of a cosmological constant. This fact has led to many
discussions on the equivalence of both theories at classical and quantum
levels. Here we present an analysis focused on the classical scalar
perturbations around a cosmological background. The discussion is extended for
the case where a non-minimal coupled scalar field is introduced. Our results
indicate that the equivalence is not verified completely at perturbative level.
