Police said on Friday they had arrested a 28-year-old man after a homeless woman was robbed in Kowloon City last week.
Officers said the victim, 74, lost valuables and HK$16,000 in cash.
The woman said she has been collecting used cardboard for the past 10 years and the cash stolen was given to her by her son.
Police said they were looking for another suspect in connection with the case.