关于 (guānyú) and 对于 (duìyú) seem similar, since both of these prepositions are used to point to specific people or things. However, when taking a closer look, the things they discuss and the angles they take are different.
Different Points of Emphasis
对于 looks towards the object referred to, and usually the person or object referred to has adopted a certain attitude or has come into some kind of situation.
Examples with 对于
- 对于 那 个 人 我 并 不 了解。 I just don't understand that person.
- 对于 我们 的 工作 表现，老板 很 满意。 The boss is very satisfied with our performance.
- 对于 这 件 事情 他 没什么 看法。 He doesn't really have any opinion about this matter.
关于 emphasizes a range, and it introduces all things that are related to it.
Examples with 关于
- 他 昨天 发表 了 一个 关于 中国 经济 的 演讲。 He made a speech about Chinese economy yesterday.
- 我 需要 写 一 篇 关于 中 美 文化 差异 的 文章。 I need to write an article about the difference between China and America.
- 关于 你 辞职 的 申请，公司 还 在 考虑。 About your resignation, the company is still considering.
- 关于 孩子 的 教育，她 跟 丈夫 的 看法 很 不 一样。 About children's education, her opinion is very different from her husband's.
Notice that in the second example, if you were just to say "老师说有很多毛病" without first pointing out what it's referring to 学习方法, it would cause some confusion.
关于 (guānyú) can also be used in the title of an article.
Examples
- 关于 部门 调整 和 人事 安排 "Regarding Department Adjustments and Human Affairs"
- 关于 新年 放假 的通知 A Notification regarding New Year vacations.
Situations where they are the same
When the point emphasized is pretty clear (whether it be a range or a specific thing), then you can use either.
Examples
- 关于/对于这份决议，大家还有什么补充吗？ Is there anything that anyone wants to add to this decision?
- 关于/对于这个问题，你们还有什么意见？ As for this problem, do you guys still have some thoughts?
Sources and further reading
Books
- 对外汉语教学语法释疑201例 (对于 vs 关于 p.202)
- New Practical Chinese Reader 4 (新实用汉语课本4) (p. 61)
Dictionaries
- 现代汉语词典（第5版） (关于p.501，对于 p.346)