There is no difference among 立刻, 立即, 马上 in terms of meaning, but 马上 is used more in speaking Chinese, it's more casual, while 立刻 and 立即 are more formal, and used more in written Chinese or formal occasion, for example, when schools use speakers to announce a gathering order, it might say: "...请立即（立刻）到操场集合！“(Please gather in the play ground immediately!)

these three Chinese words all means RIGHT NOW. on meaning expression, they are same. As to the usage, the words "立刻“ and "马上” both could be used alone. eg. clean the floor. right now! 清洁地板。 立刻/马上！

评论里面的zhang 说的比较正确。 马上是最口语化的表示。立即和立刻是比较书面化的表达。 但是个人并不认为这三个词语可以从时间间隔上面有所区分。

三个词肯定是有区别的。但不一定是上面说的那样。 你把这个错改了，立刻。这里一般不说：立即。 但，判处死刑，立即执行。很少会说成马上执行或立刻执行。 不过对一般口语来说，只用马上也不会有大错。

谢谢你们！