This chapter introduces both the requirements and challenges for an efficient use of formal methods in quantum computing and the current most promising research directions. While the recent progress in quantum hardware opens the door for significant speedup in cryptography as well as additional key areas (biology, chemistry, optimization, machine learning, etc), quantum algorithms are still hard to implement right, and the validation of quantum programs is a challenge. As an alternative strategy, formal methods are prone to play a decisive role in the emerging field of quantum software. The chapter also introduces several existing solutions for the formal verification of quantum compilation and the equivalence of quantum program runs. The vast majority of quantum algorithms are described within the context of the quantum co-processor model, i.e. an hybrid model where a classical computer controls a quantum co-processor holding a quantum memory.