Sleep is influenced by many extrinsic and intrinsic factors, including aging. Adequate sleep quality and quantity are paramount for optimal brain health and cognitive function. Many sleep disorders are associated with cognitive dysfunction. Moreover, sleep disorders and disturbances have shown specific associations with altered regional brain structural patterns, mostly measured with magnetic resonance imaging (MRI), as well as abnormalities in specific functional neuroimaging measures. Given increasing risk of neurocognitive impairment and of dementia with aging, is it important to understand the associations between sleep and its disorders and neurodegeneration. In this chapter, the brain imaging and cognitive profiles of most common sleep disorders and disturbances are discussed, including hypersomnolence, short and long sleep duration, insomnia, circadian disorders, obstructive sleep apnea (OSA), restless leg syndrome (RSL), and REM sleep behavior disorder (RBD). The interplay between sleep disorders and changes in brain structure and function is complex and appears to be bidirectional.