Respondent = a person who replies to something, especially one supplying information for a questionnaire.

• The majority of respondents were of the opinion that there was no chance for an early poll.
• Some of the respondents were not willing to give more details about the controversial issue.

Correspondent = a person employed to report for a newspaper or broadcasting organisation;  reporter, journalist etc.

• A football correspondent.
• He was a war correspondent.
• Their foreign correspondent passed on more information regarding the outcome of the election.