Folders in external hd do not show up on mac

i saved a bunch of files in three folders from a pc into a external hard drive
but when i plugged it into my mac osx only one of the folders were visible ....
so when i plugged it back into the pc they were all there !
the hd is formatted as mac journaled ( by disk utility of mac )
so i should still be able to read the data even if i cant write

please help ...