The T20 series succeeded the 600 series, adding new features such as S-Video output, an Ethernet port, and the UltraBay 2000 hot-swappable bay.

The ThinkPad T23 was also the first ThinkPad laptop model to offer an optional WiFi connection via a mini-PCI card, using wireless antennas which were built into the lid on select upper-end models.

One common problem of the earlier T20 series was a hardware defect which caused the machine to suddenly stop working and begin blinking the hard drive and power indicators.

Another common issue with the T23 was that one of the coils, near the CPU, could break off the motherboard due to cold solder joints.

This caused multiple issues, including the inability to boot or hard lockup/freeze.