<p>Drainage trenches are widely adopted for the stabilization of slow-moving or dormant landslides in fine-grained soils. Their design is usually carried out through abacuses or numerical analyses based on models that assume the soil surrounding the trenches to be a homogeneous and isotropic porous continuum. This approach, however, often fails to account for the role of certain typical yet apparently minor features of landslide bodies, such as the basal shear zone or soil heterogeneities, which are part of the hydraulic system and can significantly affect the groundwater regime. Some considerations on the influence of such features on the effectiveness of drainage trenches extending down to the sliding surface are presented in this paper. The study reports the results of finite-element seepage analyses, which show that the hydraulic properties of the basal shear zone, as measured in some earthflows or inferred from soil-fabric description in slides, together with those of heterogeneities such as thin soil layers within the landslide body, may lead to a response that is significantly different from, and more favourable than that predictable by conventional approaches. In particular, the study results highlight important implications for drainage trenches design. In fact, because the permeability of both types of features differs from that of the surrounding landslide material, either exceeding or falling below it, they may enhance groundwater flow towards the trenches. Consequently, trench efficiency under steady-state conditions may increase significantly, allowing a wider trenche spacing. The analyses also indicate, however, that the time required to reach the steady-state may, in some cases, be longer than that associated with homogeneous soil conditions.</p>