The spirit of Code Review is to get actual code from actual projects you're working on, peer reviewed by a community.
If the entire code in your question is this little snippet:
if(a) { if(b) { //some statement(s) } } else if(c) { //some statement(s) (the same ones as in the other block) }
Then the question isn't about reviewing your code, it's about ways to write the code for a hypothetical conditional statement, where a hypothetical code block would be duplicated in two branches.
IMHO, the "answer" is something like: if(a && b || !a && c) { /* some statement(s) */ }.
This isn't a code review question, I think it would be more on-topic on Programmers.StackExchange.
On the other hand, if you supplied your actual code, with the actual repeated code blocks, and asked "how bad is duplicating a code block?", answerers could actually review your code, and address the duplication concern.
Just providing a "sample code" snippet to illustrate a hypothetical situation, is off-topic IMHO, because it goes against the spirit, it's too high-level and more on Programmers.StackExchange's grounds.