PM,
i vote for running them the same way.
FW

Ditto. My bead board ceiling is parallel to the floor boards...

Just to be contrary :-) our ceiling beadboard (which we're re-staining this very weekend!) runs the length of the porch while the floorboards run widthwise. The beadboard is in normal 8' lengths, with the ends "staggered" the same way you'd do a hardwood floor. Here's a lousy picture of the original installation - we had to take up the floor and do structural repairs beneath due to decades of neglect, but the original ceiling is intact:

We know this floor shown was the original floor, or real dang close to it, because the odd square on the floor next to the front sawhorse is the hatch for the coal chute.

I really thought I'd posted here already ! I'll try again.
Our 1920s home has 4 porches, two on the front and two on the back. The front ones run the width of the house the back are a little shorter. On the upstairs porches the beadboard on the ceiling runs the length of the porch and on the downstairs porches it runs width way. The floor boards all run width ways. Both look fine, especially the ones that are repainted and restored. I've always thought it was curious. Maybe they did the upper porches first and then had a bunch of shorter pieces.
kathy

Our den v-groove ceiling runs straight while the antelope printed carpet and the floor tile run at a 45. The v-groove on the porch ceiling and the porch floor tile are both installed at a 45 degree angle.
Monica

This is total speculation, but does the direction of the floor and ceiling joists make a difference as to which way the tounge and grove runs?

That's just what I was thinking - it would be determined by the direction of the joists. And if you decide to do it differently, you'd have to install a framework of hanger boards and thus lose an inch or two of ceiling height.

KarinL

you would install furring strips to ceiling joists to nail the beadboard to.

I think the floor and ceiling joists determine as acc0406 suggested. That would explain why the downstairs porches on my house run the same way as the floor (including the floors of the porches immediately above).
I actually haven't noticed a difference in the perception of space due to the difference. But that may be because all 4 porches have completely different uses and furnishings.
kathy

I'm going to take the easy way out and do 48x48 squares going alternate directions and use 1x4's over the seams. I'm going to use beadboard wallpaper. I have an inspiration picture but I don't have very good luck posting pictures here.