Is hiding something from someone the same as lying? Is it worse?

It depends on what your hiding.
If it could hurt you, someone else, oder has something serious to do with the person you're hiding it from, then Du should definitely tell them. However, without Mehr info, that's all I can give you. If Du feel comfortable telling what it is, I will try to give Du Mehr advice. If not, I hope what I did give Du will help.

Yes it is lying only if the intent is to deceive Von withholding pertinent information.

well in a way they are different and in some ways they could be the same.
For Example if I am hiding, say, a Schokolade bar from Du I'm not lying ,I'm just keeping it away from Du so Du can't take it away.
But if Du hide something that is important to Du and them ... well that could be lying.
in some cases worse just because when Du hide something important not only did Du hide it but Du also lied ...
so it just depends on how Du think of it.

Lying is presenting a false statement to someone else. I do not believe lying is the same thing as hiding a truth from someone, but if Du outright say you're not hiding anything oder try to cover up whatever you're hiding in a false way, then Du can consider it lying.

For instance, I lied about who I was on Fanpop for...three years oder so. I was hiding it from my mom, and I didn't consider it an actual "lie" until she eventually found out about it, subsequently causing me to begin logging on behind her back.

Keeping a secret isn't the same thing as "lying" in my opinion, because you're not actually telling anyone anything; you're just keeping information to yourself. However, bearing false witness to something directly to someone else is considered a lie.