- forget + to-infinitive = not to remember to do something We use the structure to talk about necessary actions and whether we do them or not: 'You forgot to sign the cheque. ~ Oh, sorry.' 'I forgot to lock the doors.' - We use a gerund (forget doing something) to talk about memories of the past. (it is possible only when 'forget' is in the negative) 'I'll never forget waiting for bombs to fall.' - To forget about something = to stop thinking about something 'Let's forget about who was more to blame –it's all past history.' - It can also be followed by noun clauses beginning by 'how', 'why', etc. = to lose the memory of something 'You never forget how to swim.' 'I've forgotten where I put it.'

C.Bunny.C is correct except for the last example. you cannot say 'forget doing something.' this is an incorrect use of grammer because forget is in the past tense and doing is in the present tense. if you are referring to the past you could say "i forgot to do something" or for the present "i have forgotten to ___" just remember that "forgot" refers to the past and "forget" refers to the present hope this helps

Hello Celine, this question is about the difference of the common usage between"to do"and"doing". In most cases, "to do sth"(infinite) refers to the things haven't done, and "doing" is for the things that are done already. Therefore "forget to do sth"is used in the circumstance when someone is supposed to do a certain thing, but he/she failed to make it, whereas "forget doing sth" refers to the things someone did, but he/she forgot that he did so. eg.I forgot to call him.(I didn't call him.) I forgot calling him.(I called him, but I forgot that I called.)