The review covers the current literature on the pathogenetic mechanisms of dementia in older patients with Parkinson's disease (PD). The author emphasizes that, along with the degeneration of brain structures, there are vascular changes that promote the development of mixed dementia. Neurodegenerative process and cerebrovascular pathology are in reciprocal relationship and their combination enhances the development of cognitive impairment. The cholinergic deficit is one of the key patterns of pathogenesis of dementia in PD. In this connection, the efficacy of acetylcholinesterase inhibitors: galantamine (reminil), neuromidin, rivastigmine in the treatment of PD patients with dementia is discussed. It is concluded, that correction of vascular risk factors should be administered to older PD patients with mixed dementia. A multidimensional approach with the close relationship between neurologists, psychiatrists and therapists is needed.