  The activity in the field of diffractive physics at the Large Hadron Collider
has been constantly increasing. This includes the planning for additional
dedicated apparatus -- horizontal forward proton detectors. This work focuses
on the problems related to the alignment of such devices. The effects of the
misalignment of the detectors on their geometric acceptance and on the
reconstruction of the proton kinematics are studied. The requirements for the
alignment precision are inferred for different types of possible measurements.
