  We will investigate the scenario in which the Standard Model (SM) Higgs
sector and its 2-doublet extension (called the Two Higgs Doublet Model or 2HDM)
are the "portal" for the interactions between the Standard Model and a
fermionic Dark Matter (DM) candidate. The latter is the lightest stable neutral
particle of a family of vector-like leptons (VLLs). We will provide an
extensive overview of this scenario combining the constraints purely coming
from DM phenomenology with more general constraints like Electro-weak Precision
Tests (EWPT) as well as with collider searches. In the case that the new
fermionic sector interacts with the SM Higgs sector, constraints from DM
phenomenology force the new states to lie above the TeV scale. This requirement
is relaxed in the case of 2HDM. Nevertheless, strong constraints coming from
Electroweak Precision Tests (EWPT) and the Renormalization Group Equations
(RGEs) limit the impact of VLFs on collider phenomenology.
