Mobile　opportunistic　networks　can　realize　self-organizing　communications　for　complicated　and　dynamic　scenarios,　which　makes　them　expected　to　support　various　applications.　In　this　paper,　we　investigate　how　far　the　data　can　reach　within　time　t　(i.e.　the　dissemination　distance),　which　reveal　the　tempo-spatial　data　dissemination　properties　of　mobile　opportunistic　networks.　Our　investigations　are　taken　under　the　Brownian　motion　model.　Because　the　Brownian　motion　model　can　be　viewed　as　a　limiting　case　of　the　random　walk　mobility　model　and　the　markovian　mobility　model,　our　analytical　results　can　be　easily　extended　to　these　mobility　models.　In　detail,　we　obtain　the　upper　bound　and　the　lower　bound　of　the　distribution　of　the　dissemination　distance　for　the　one-copy　case　and　the　multiple-copy　case,　which　provide　the　potential　of　mobile　opportunistic　networks　to　support　the　services　that　may　involve　time　and　location　sensitive　data　dissemination.