Mandarin speakers may have problems with the following minimal pairs:
/ɪ/and/i:/ as in sit/seat or it/eat (/ɪ/ is short, while /i:/ is long). All China
/w/ and /v/ as in west/vest All China.
/w/ and /r/ as in witch/rich Cantonese speakers, especially from Hong Kong.
/l/ and /r/ as in light/right. Common all over China, but less so with speakers of standard Mandarin, which has two individual sounds which are roughly the same as the English sounds.
/f/ & /h/as in funny/honey Guangdong, Fujian, Hunan, Hubei, Sichuan & other regions.
/n/ & /l/ as in name/lame. Guangdong, Hubei, Hunan, Fujian, Zhejiang & others.
Schwa /ə/ added at the end of words or syllables. Common in many parts of China. Less common in Southern China, where speakers are more likely to drop final consonants.