Exhibit 8.1

List of Significant Subsidiaries and Principal Consolidated Affiliated Entities*

Significant Subsidiaries	Jurisdiction of Incorporation
21ViaNet Group Limited	Hong Kong
21Vianet Mobile Limited	Hong Kong
Hongkong Fastweb Holdings Co., Limited	Hong Kong
Diyixian.com Limited	Hong Kong
DYXNet Limited	Hong Kong
Dermot Holdings Limited	British Virgin Islands
WiFire Group Inc.	British Virgin Islands
Fastweb International Holdings	Cayman Islands
21Vianet Data Center Co., Ltd.	PRC
21Vianet Anhui Suzhou Technology Co., Ltd.	PRC
Joytone Infotech Co., Ltd.	PRC
21Vianet (Foshan) Technology Co., Ltd.	PRC
Abitcool (China) Broadband Inc.	PRC
21Vianet Hangzhou Information Technology Co., Ltd.	PRC
Beijing Fastweb Technology Co., Ltd.	PRC
Shenzhen Diyixian Communication Co., Ltd.	PRC
Principal Consolidated Affiliated Entities
Beijing Yiyun Network Technology Co., Ltd. (previously known as Beijing aBitCool Network Technology Co., Ltd.)	PRC
Beijing iJoy Information Technology Co., Ltd.	PRC
Shanghai iJoy Information Technology Co., Ltd.	PRC
Beijing 21Vianet Broad Band Data Center Co., Ltd.	PRC
Dongguan Asia Cloud Investment Co., Ltd.	PRC
Dongguan Asia Cloud Network Technology Co., Ltd.	PRC
Dongguan Asia Cloud Broad Band Service Co., Ltd.	PRC
Beijing Chengyishidai Network Technology Co., Ltd.	PRC
Beijing Yilong Xinda Technology Co., Ltd.	PRC
Guangzhou Gehua Network Technology and Development Co., Ltd.	PRC
Langfang Xunchi Computer Data Processing Co., Ltd.	PRC
Sichuan Aipu Network Co., Ltd.	PRC
Beijing Tianwang Online Communication Technology Co., Ltd.	PRC
Beijing Fastweb Network Technology Co., Ltd.	PRC
aBitCool Small Micro Network Technology (BJ) Co., Ltd.	PRC
Shanghai Guotong Network Co., Ltd.	PRC
Shanghai Blue Cloud Technology Co., Ltd.	PRC

* Other entities of 21Vianet Group, Inc. have been omitted from this list since, considered in the aggregate as a single entity, they would not constitute a significant subsidiary.