Frontotemporal dementia (FTD) is the second most common form of young-onset dementia after Alzheimer’s disease. It refers to a group of disorders characterized by progressive behavioral and/or language impairment, dramatically affecting the lives of patients and their relatives. The large clinical and neuropathological diversity of the FTD spectrum challenge the recognition of the fundamental processes driving disease initiation and progression. Over the past decades, major advancements in genomics and affiliated research areas have provided a wealth of information regarding the mechanisms underlying FTD. This PhD dissertation highlights these developments and broadens our knowledge by examining both genes and proteins implicated in the disease. It provides further characterization of known genes, describes novel genes and genetic variants, and sheds light on relevant protein alterations in affected brain tissues of patients. Altogether, it contributes to our understanding of the molecular underpinnings of FTD and related disorders, essential for future development of diagnostic biomarkers and therapeutics.