Exhibit 21

QUANTUM CORPORATION

SUBSIDIARIES OF THE REGISTRANT

1. ATL Products Ltd., a United Kingdom corporation

2. Quantum International Inc., a Delaware corporation

3. Quantum Peripheral Products (Ireland) Ltd., an Ireland corporation

4. Quantum Peripherals (Europe) Sárl., a Swiss corporation

5. Quantum Peripherals (Malaysia) Sdn. Bhd., a Malaysian corporation

6. Quantum Distribution (UK) Limited, a United Kingdom corporation

7. Quantum Storage Australia Pty. Ltd., an Australian corporation

8. Quantum Storage Germany GmbH, a German corporation

9. Quantum Storage France, a French corporation

10. Quantum Storage Japan Corporation, a Japanese corporation

11. Quantum Storage Singapore Pte. Ltd., a Singapore private company

12. Quantum Storage Solutions (M) Sdn. Bhd., a Malaysian corporation

13. Quantum Storage UK Ltd., a United Kingdom corporation

14. Certance Holding Corporation, a Delaware corporation

15. Certance LLC, a Delaware limited liability company

16. Certance (US) Holdings, Inc., a Delaware corporation

17. Certance International, a Cayman Islands company

18. M4 Data (Holdings) Ltd., a UK corporation

19. Advanced Digital Information Corporation, a Washington Corporation

20. ADIC AG, a Swiss corporation

21. Quantum GmbH, a Germany corporation

22. ADIC Germany GmbH & Co. KG, a Germany corporation

23. ADIC Germany Beteiligungs GmbH, a Germany corporation

24. ADIC International Holdings, a Cayman Islands company

25. ADIC Korea Co. Ltd., a Korean corporation

26. ADIC Limited, a UK corporation

27. Quantum SARL, a French corporation

28. ADIC Manufacturing, LLC, a Delaware company

29. Mountaingate Imaging Systems Corporation, a Delaware corporation

30. Pathlight Technology, Inc., a Delaware corporation

31. ADIC (US) Holdings, a Delaware corporation

32. A.C.N. 120.786.012 Pty. Ltd., an Australian company

33. Rocksoft Pty. Ltd., an Australian company

34. Rocksoft, Inc., a Texas corporation