Using LIKE expression problem.. - Mailing list pgsql-performance

Hi everybody..

     Before anything else I would like to thank all those person who answers my previous question… again thank you very much

This is my question …

     In my query .. Select * from table1 where lastname LIKE  ‘PUNCIA%’..

In the query plan ..it uses seq scan rather than index scan .. why ? I have index on lastname, firtname…

Thanks