We are arriving in Paris by plane. Can we catch a train from the airport to Brussels or do we need to go into Paris and catch the train from there?
Yes, you can go direct from CDG airport to Brussels. There are TGV trains that do this route. http://www.tgv-europe.com
If your flight arrives at the right time, you can take a TGV from CDG to Brussels. Direct TGVs depart at 07:47, 10:10, 12:35, 16:03, 16:39, 17:40, 18:49, and 20:04.
If you want to ride the Thalys to Brussels instead of the TGV, it departs from the Gare du Nord in Paris. I did; it's a dream!
Thanks for the answers everyone but wha tis the difference between TGV and Thayls? Cost? Time?
Both TGVs and Thalys trains are high-speed trains. Your only choice for Paris-Brussels is Thalys trains.
IMO, your best route is a direct TGV from CDG to Brussels. The trip takes around 1hr40min. The standard 2nd class fare is €73. Booked well in advance (up to three months allowed) at www.tgv-europe.com, you can get a Prem's fare as low as €29. However, Prem's tickets are non-exchangeable and non-refundable so you have to allow a generous connection time. If your plane is late and you miss your train, your ticket will be worthless.
It takes about 40 minutes to get from CDG to Gare du Nord on the RER B. The fare is €8.50. It takes around 1hr20min on a Thalys train from Gare du Nord to Brussels. The standard 2nd class fare is €88. Booked well in advance (up to 90 days allowed) at www.thalys.com, you can get a Smoove fare as low as €25. That ticket also is non-exchangeable and non-refundable.
Discount fare tickets sell out fast. To get one, book ASAP.
We all have different priorities in our choices when making travel plans.
While it is true that some TGV's go direct from CDG to Brussels, most do not. They go first to Lille and the travelers have to change trains to the Eurostar (coming from London) for the final leg to Brussels.
Actually there are great differences in the service provided by Thalys compared to TGV; and these differences are found in the quality of comfort and service.
I recommend a first class ticket on the Thalys. This fare includes full beverage and meal service at your seat.
The service on the Thalys is impecable!
Thalys also has free WiFi for first class customers. But when traveling second class, the comfort level of Thalys vs TGV is mostly interchangeable.
If cost is a factor, look at Eurolines.com. Rates can be as low as 13E one way, booked early.