This paper presents an analysis of relations between player motivation and behavior in a Massively Multiplayer Online Role-Playing Game (MMORPG). We examine player behavior in terms of when, how much, and what they do in the virtual world. Player motivation is measured in terms of percentile ranks of motivational components for MMORPG players defined by Nick Yee. Player behavior is described through previously defined action categories for MMORPGs (Trading, Questing, Dungeons, Raiding, Player versus Player (PvP) Combat, and Communication). We conduct a player survey and perform measurements on the client side for a group of 104 players of a popular MMORPG-World of Warcraft (WoW), and discover that there are strong patterns in player behavior and significant relations between specific motivational components and players' actions in the virtual world. Additionally we examine the importance of both voice and textual (chat) communication in MMORPGs, note that communication makes a significant portion of average player's playtime, and that voice communication is used by a large portion of players. Through understanding of the relations between player behavior and generated network traffic we can describe and anticipate the traffic better, on the scale of one, as well as a large number of users. We believe that the results of this study may be used for improving the models and prediction of MMORPGs' network traffic.