Narrative:

I was PF on approach to sea. WX was 2100 ft scattered, visibility 10 mi in haze. On left downwind abeam at about 5000 ft, approach controller pointed out a 737 at 11 O'clock (I don't remember the reported range). We spotted an aircraft at that azimuth (incidently winds were easterly aloft) and reported that we had the reported aircraft in sight, ATC told us that he was for runway 34R, we were cleared for visual runway 34L. We turned base reference the aircraft we thought to be our traffic. While turning base, we spotted another aircraft behind the one we thought was our traffic. ATC, simultaneously pointed out our mistake, as it turned out the second aircraft was our true traffic. Both aircraft were for runway 34R, so we continued for an uneventful landing runway 34L, although we were aligned for runway 34L ahead of our traffic for runway 34R. I continued to visually reference this traffic slightly behind and to our right on final. We followed the wrong aircraft initially, and that is our fault. However, the point out that ATC gave us certainly described the approximately position of the aircraft that we mistakenly idented, an A-320. ATC never pointed this aircraft out to us, a simple comment that would have prevented our mistake, ie, 'you'll see 2 aircraft on final, the first is a A-320 the second a B737 your traffic is the second.'

Related reports:

Google
 

Original NASA ASRS Text

Title: VISUAL SEPARATION ATTEMPTED BY APCH CTLR WITH TA GIVEN. WRONG TFC SIGHTED BY FLC.

Narrative: I WAS PF ON APCH TO SEA. WX WAS 2100 FT SCATTERED, VISIBILITY 10 MI IN HAZE. ON L DOWNWIND ABEAM AT ABOUT 5000 FT, APCH CTLR POINTED OUT A 737 AT 11 O'CLOCK (I DON'T REMEMBER THE RPTED RANGE). WE SPOTTED AN ACFT AT THAT AZIMUTH (INCIDENTLY WINDS WERE EASTERLY ALOFT) AND RPTED THAT WE HAD THE RPTED ACFT IN SIGHT, ATC TOLD US THAT HE WAS FOR RWY 34R, WE WERE CLRED FOR VISUAL RWY 34L. WE TURNED BASE REF THE ACFT WE THOUGHT TO BE OUR TFC. WHILE TURNING BASE, WE SPOTTED ANOTHER ACFT BEHIND THE ONE WE THOUGHT WAS OUR TFC. ATC, SIMULTANEOUSLY POINTED OUT OUR MISTAKE, AS IT TURNED OUT THE SECOND ACFT WAS OUR TRUE TFC. BOTH ACFT WERE FOR RWY 34R, SO WE CONTINUED FOR AN UNEVENTFUL LNDG RWY 34L, ALTHOUGH WE WERE ALIGNED FOR RWY 34L AHEAD OF OUR TFC FOR RWY 34R. I CONTINUED TO VISUALLY REF THIS TFC SLIGHTLY BEHIND AND TO OUR R ON FINAL. WE FOLLOWED THE WRONG ACFT INITIALLY, AND THAT IS OUR FAULT. HOWEVER, THE POINT OUT THAT ATC GAVE US CERTAINLY DESCRIBED THE APPROX POS OF THE ACFT THAT WE MISTAKENLY IDENTED, AN A-320. ATC NEVER POINTED THIS ACFT OUT TO US, A SIMPLE COMMENT THAT WOULD HAVE PREVENTED OUR MISTAKE, IE, 'YOU'LL SEE 2 ACFT ON FINAL, THE FIRST IS A A-320 THE SECOND A B737 YOUR TFC IS THE SECOND.'

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.