Beauvais Airport is about 80km (50 miles) Paris.
Bus departures from Port Maillot are scheduled to leave 3 hours before the departure of the relevant flight. (You're advised to be at the bus stop 3 hours 15 minutes prior to the flight time).
To check your bus departure time, see here:
http://www.aeroportbeauvais.com/horaire_bus.ph p?lang=eng
Porte Maillot is on the fringe of the city centre, served by Metro Line 1 (or RER Line C to Neuilly-Porte Maillot):
http://www.aeroportbeauvais.com/img/plan_paris .gif
Tickets are �13 each way. They can be purchased on the bus or pre-booked here:
http://tickets.aeroportbeauvais.com/us/index.c fm
To get around Paris, consider buying a Paris Visite ticket:
http://www.ratp.info/touristes/index.php?langu e=en
Chris