Fifty-four species of lady beetles were collected from three Chinese hemlock species, Tsuga dumosa (D. Don) Eichler, T. forrestii Downie and T. chinensis (Franchet) Pritzel, in Yunnan, Sichuan and Shaanxi provinces of China as part of a search for natural enemies of the hemlock woolly adelgid, Adelges tsugae Annand. Twenty new species are described: Clitostethus wenbishanus Yu, Scymnus (Neopullus) ningshanensis Yu and Yao, S. (N.) lijiangensis Yu, S. (N.) lycotropus Yu, S. (N.) nigromarginalis Yu, S. (Parapullus) tsugae Yu and Yao, S. (Scymnus) unciformis Yu, S. (S.) paracrinitus Yu, S. (Pullus) nigrobasalis Yu, S. (P.) baoxingensis Yu, S. (P.) gucheng Yu, S. (P.) geminus Yu and Montgomery, S. (P.) heyuanus Yu, S. (P.) robustibasalis Yu, S. (P.) jaculatorius Yu, Pseudoscymnus heijia Yu and Montgomery, P. ocellatus Yu, Shirozuella quadrimacularis Yu, and Sh. nibagou Yu. New synonyms placed here are: Oenopia yunlongensis Jing for O. deqenensis Jing, and O. pomiensis Jing, O. gonggarensis Jing and O. picithoroxa Jing for O. billieti (Mulsant). Harmonia quadripunctata (Pontoppidan) is a new record for China. Keys are provided to separate the known species of Clitostethus Wiese, Scymnus (Neopullus) Sasaji, and Scymnus (Scymnus) Kugelann in China. Nine species are recorded as predators of the hemlock woolly adelgid: Oenopia billieti (Mulsant), Adalia conglomerata (L.), Calvia championorum Booth, P. ocellatus, S. (N.) camptodromus Yu et Liu, S. (N.) sinuanodulus Yu et Yao, S. (N.) ningshanensis, S. (P.) yunshanpingensis Yu, and S. (P.) geminus.