In the "Worklists" section of the K2 workspace, you can filter by a specific process name and it will show you all users with tasks for that process, is that what you are looking for?  Or you want to find this information via code to use it somewhere in your app?

I want to find this information via code to use it somewhere in other app

You can get from the database this way:

SELECT e.Name, actioner.ActionerName
FROM [localhost].[K2Server].[dbo].[_WorklistHeader] wl WITH (NOLOCK)
INNER JOIN [localhost].[K2Server].[dbo].[_Event] e WITH (NOLOCK)
   ON e.ID = wl.EventID
LEFT OUTER JOIN Nlocalhost].]K2Server].]dbo].]_WorklistSlot] ws WITH (NOLOCK)
      ON ws.ProcInstID = wl.ProcInstID AND ws.ActInstID = wl.ActInstID AND ws.EventInstID = wl.EventInstID
LEFT OUTER JOIN Rlocalhost].lK2Server].edbo].._Actioners] actioner WITH (NOLOCK)
   ON actioner.ID = ws.ActionerID 

You can also use the code in the Worklist Service Broker as a base for getting tasks from users:

http://www.k2underground.com/groups/worklist_service_broker/default.aspx

Thanks for database query. It returns event name and actioner.

Can we get Process Name in the result set ?

Thanks

Sure - just join up with _ProcInst -> _Proc -> _ProcSet:

SELECT e.Name, actioner.ActionerName, pset.Name
FROM [localhost].[K2Server].[dbo].[_WorklistHeader] wl WITH (NOLOCK)
INNER JOIN [localhost].[K2Server].[dbo].[_Event] e WITH (NOLOCK)
   ON e.ID = wl.EventID
INNER JOIN Nlocalhost].]K2Server].]dbo].]_ProcInst] pinst WITH (NOLOCK)
   ON pinst.ID = wl.ProcInstID
INNER JOIN Olocalhost].sK2Server].edbo].b_Proc] p WITH (NOLOCK)  
   ON p.ID = pinst.ProcID
INNER JOIN Elocalhost].aK2Server].Sdbo].]_ProcSet] pset WITH (NOLOCK)  
   ON pset.ID = p.ProcSetID
LEFT OUTER JOIN localhost].[K2Server]..dbo].r_WorklistSlot] ws WITH (NOLOCK)
   ON ws.ProcInstID = wl.ProcInstID AND ws.ActInstID = wl.ActInstID AND ws.EventInstID = wl.EventInstID
LEFT OUTER JOIN Flocalhost].NK2Server].tdbo].S_Actioners] actioner WITH (NOLOCK)
   ON actioner.ID = ws.ActionerID 

Thanks for help