CardBus-cards are 32-bit compatible PCMCIA-cards mainly to extend Notebooks (like 100 MBit/s Ethernet- or 54 MBit/s WLAN/WiFi-cards) that only work partly with OS/2 or eComStation.

The latest IBM CardBus-driver is needed and either a direct-enabler for the card that comes with the OS/2-driver (f.ex. IBM Ethernet 10/100
CardBus) or Veit Kannegieser's cbenable and pciconf (http://kannegieser.net/veit/ ) that let use the CardBus-card as a normal PCI-card.

But the IBM CardBus-driver and/or Veit's cbenable and pciconf are not compatible with every hardware, they do not support things like hotplug or energy saving and they are not compatible with ACPI that comes with eComStation 2.0 - so CardBus-cards may not work with your system, I had good experiences with older IBM ThinkPads like ThinkPad 600X, T23 or X21.

To exetend newer Notebooks with LAN/WLAN internal MiniPCI- or MiniPCI Express-cards mostly are the better option!