I'm trying to figure out what's the difference between several CALL (or PUT) options for the same underlying, that have the same strike price and expiration? I've see these listed for TWX, WFC, (two each), CM (3) etc. Also, they are sometimes listed, sometimes not. For example, CM: Morningstar lists 3 CALLs and PUTS for APR 09 with strike prices 35 and 40: http://quote.morningstar.com/Option/Options.aspx?ticker=cm BUT CBOE lists only one of each: http://www.cboe.com/DelayedQuote/QuoteTable.aspx and so does Yahoo! Finance: http://finance.yahoo.com/q/op?s=CM So what's the deal here? What are these duplicate options? LEAPS? Why doesn't CBOE list them? Where's the "real" data? How can I find which one was issues in which year? Why do they have such different premiums, if they're all supposed to expire in April 09? Why can I trade only one of the CM 30 APR 09 CALL/PUT options in InteractiveBrokers TWS?