Purpose: The aim of this study was to validate the Korean version of World Health Organization Disability Assessment Schedule 2.0 (KWHODAS 2.0) in 12 item-self administered version (12-self). Methods: The KWHODAS 2.0 and Korean Functional Rating index (KFRI) were tested for internal consistency, ceiling and floor effects, and concurrent validity in 111 patients with low back pain and/or neck pain. Results: A very high level of internal consistency was shown for both instruments; ${alpha}$=0.96 with KWHODAS 2.0; 12-self and ${alpha}$=0.97 for KFRI. No ceiling and/or floor effects were found in both the instruments. The KWHODAS 2.0 and KFRI were highly correlated (r=0.77), and the relationship of each item between KWHODAS 2.0 and KFRI was ranging from r=0.09 to 0.72. Conclusion: We conclude that the KWHODAS 2.0: 12-self and KFRI are reliable and are valid instruments for the measurement of disability in Korean speaking patients with low back and/or neck pain. Both instruments, the KWHODAS 2.0; 12-Self and KFRI are now suitable for use in clinical practice and research applications.