Girona is approximately 55 miles from Barcelona.  The main way from Girona Airport to Barcelona is the Barcelona Bus to Barcelona Estacio del Nord (Barcelona's main bus station).  The bus is timed to meet Ryanair flights and will wait for delayed flights.  The fare is €16 one way, €25 return/round trip (Valid for 30 days).  Journey time is 1 hour 10 minutes.

It is possible to take a taxi to Barcelona, but this will cost around €100 and won't be any quicker.

If travelling from Barcelona to Girona consider the Renfe. Takes just over an hour and costs less than 7euros.

Visiting Girona and arriving at Girona airport the cheapest way to go to Girona city is by bus. The price of a return ticket from the airport to Girona is only 3,40 euro. So if you want to visit Girona don't fly to Barcelona. From Girona there is a direct train connection to Barcelona, if you want to visit Barcelona for one day.

 You can also use one of the AVE trains.