The role of orthographic neighbors (e.g. bank - tank) in word processing has been discussed in many experimental studies. However, these studies have been conducted on a limited pool of languages, and many important questions are still unresolved. After creating a lexical database StimulStat that contains various neighborhood parameters for Russian, we conducted the first experiment with substitution neighbors in Russian. We used lexical decision task with priming, and manipulated the following factors: whether the prime is more or less frequent than the target, whether the prime is a nominative singular (primary) form or an oblique form, and whether the substituted letter is word-final or in the middle of the word. The results suggest that noun forms undergo morphological decomposition at a very early stage and shed new light on the process of activating candidates during lexical. The results also have practical significance because it is well known that spelling errors are influenced by neighborhood effects.