  This thesis is based on some selected topics in open topological string
theory which I have worked on during my Ph.D. It comprises an introductory part
where I have focused on the points most needed for the later chapters, trading
completeness for conciseness and clarity. Then, following [12], we discuss
tadpole cancellation for topological strings where we mainly show how its
implementation is needed for ensuring the same "odd" moduli decoupling
encountered in the closed theory. Next we move to analyse how the open and
closed effective field theories for the B model interact writing the complete
Lagrangian. We first check it deriving some already known tree level amplitudes
in term of target space quantities, and then we extend the recipe to new
results; later we implement open closed duality from a target field theory
perspective. This last subject is also analysed from a worldsheet point of view
extending the analysis of [13]. Some ideas for future research are briefly
reported.
