The general problem of Quantum Dissipation will be stated in the context of an electron in a magnetic field. We will show how dissipation makes the system move from the Landau regime to the Bohr-Van Leeuwen regime, which may be viewed as a coherence to decoherence transition. We will also discuss the specific heat and make some remarks on the Third Law of Thermodynamics. The problem allows us to also compare and unify two different approaches to Statistical Mechanics: the Gibbs and the Einstein (Quantum Brownian Motion) approaches.