Our theoretical studies of fluctuations in the vicinity of phase and structural transitions and the fluctuation-induced force in two model confined nematic liquid crystals are briefly reviewed. We focus on the paranematic phase characterized by substrate-stabilized wetting layer and on nematic films frustrated by competing surface fields. Depending on temperature, anchoring strengths, and frustration, the fluctuation-induced force can be either short- or long-range, either attractive or repulsive, and it exhibits a pretransitional increase.