All this week on Newsround we're looking at the five things YOU told us worry you the most and that includes terrorism.
Terrorism is when people use violence - like bombs - to make people behave the way they want. Usually it's connected to politics.
So do you worry about terrorism or is it something that you don't think about?
If you worry, was there something that happened to spark your concerns?
Unfortunately this topic is now closed but there are Comments pages on other subjects on the main Chat index.
"I don't think it's worth worrying about, there is only a small chance of it happening."
Kaleem, 10, Worcester, England
"No, I've lived in Afghanistan and I feel really safe at home here in Wales."
Hanna, 10, Dyfed, Wales
"No, I don't worry because I know that the people who run the country are trying their hardest and there is not a lot I could do anyway, so why clog up my mind?"
Claire, 11, Sheffield, England
"I hate going on the tube. I am always looking around me and worrying. I love London but hate the tube."
Georgia, 13, Hertford, England
"I sometimes worry, but not all that much, what you have to remember is that the police are protecting everywhere now."
Georgina, 13, Kent, England
"I am worried because I hear about lots of terrorism on the news."
Georgia, 10, Glasgow, Scotland
"Terrorism is very rare but I still worry. You never know when it can happen. It affects innocent lives."
Harriet, 10, Stockport, England
"I hate terrorism. I worry when it comes on the news and I'm going on holiday."
Heather, 10, Dundee, Scotland
"I am very worried about terrorism because I am always scared that there will be bombs, violence and other scary things. It worries me very much."
Katie, 10, Manchester, England
"I think terrorism is terrible! Is there any point in taking the lives of innocent people? When I think of terrorism so many questions come to my head."
Tasnim, 13, London, England
"I worry sometimes. When I went on the London Underground, I got scared. Also I've never been abroad, but I don't really want to because of the idea of the plane being taken over..."
Abigail, 12, Somerset, England
"I am worried that terrorists might attack us again and I don't want 9/11 to happen again and have all those people die."
Thomas, 11, Stamford, England
"Not really, because the police are very efficient these days and have the skills and tools to find those who cause the attacks. The police help save lives!"
Kiwi, 14, London, England
"I never think about terrorism, because it's scary."
Harry, 9, Accrington, England
"I'm not worried about terrorism, because I live in the country."
Sean, 10, County Durham, England
"It's hard to understand terrorism. It's hard to understand how selfish people can be to want to end the lives of people. Terrorism does get to me, and all the time I keep feeling that I'm not in a safe environment.."
Alana, 11, Manchester, England
"Terrorism does not bother me, but it might bother others. It's all about where you live."
Chloe, 10, Kent, England
"I sometimes feel worried about terrorism when there are fights and battles with countries. It could be quite scary."
Lee, 10, Morayshire, Scotland
"Sometimes I do think about terrorism and worry. It does worry me because it is such a bad thing."
Megan, 10, Cheshire, England
"I don't live in a city so I'm not that worried about terrorism. If there has been an attack, I do as much as I can to help out."
Olivia, 13, Devon, England