The paper presents the case study of lexical selection in Alzheimer-type dementia. Lexical substitutions in poem recitation and conversations of a Russian speaker, who suffered Alzheimer-type dementia, were analyzed on the background of the lexical retrieval and slip-of-the-tongue phenomena. The classification of the substitutions is worked out on the basis of the links between a target word and its substitutions. The current context plays an essential role as natural priming for a substitution in a poem recitation. Some words have predisposition to be lost; the units belong to the figurative language or to the category of infrequent lexemes. In conversation, the patient masked failures by referring to the circumstances and appealing to the sense of humor. Positive emotions facilitate recollecting of words, involved in the description of real-life events, due to the relatively spared nondeclarative memory. The changes in the substitutions and paraphasias categories between AD stages are statistically significant.