B -> X_s l+ l- in the Standard Model and in Two-Higgs-Doublet Models

We present recent results of the rare semileptonic decay B -> X_s l+ l-. We particularly focus on higher order electroweak corrections in the Standard Model (SM) as well as O(alpha_s) corrections in Two-Higgs-doublet models (THDM), both of which are computed within an effective field theory approach. The calculation of higher order electroweak corrections reveals the presence of enhanced electromagnetic logarithms log(m_b^2/m_l^2) in the differential branching ratio. The inclusion of O(alpha_s) in the THDM reduces the scale dependence of the corresponding Wilson coefficients significantly.