It's easy to do with the floatrow
package, which is is dedicated to that, cooperates with the caption
package:
\documentclass[a4paper, 11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{floatrow}
\DeclareFloatVCode{rowsep}{\vskip 5ex}
\begin{document}
\begin{figure} [H]
\centering\floatsetup{floatrowsep = qquad, rowpostcode = rowsep}
\begin{floatrow}
\ffigbox[\FBwidth]{\caption{For the Snarks were Boojums, you see…}\label{fig:left}}
{\includegraphics[width = 0.48\textwidth]{snark.png}}
%%%%
\ffigbox[\FBwidth]{\caption{A Portrait of a distinguished author}\label{fig:right}}
{\includegraphics[width = 0.48\textwidth]{Charles-Dodgson}}
\end{floatrow}
\begin{floatrow}
\ffigbox[\FBwidth]
{\includegraphics[scale = 0.8]{sendak}}
{\caption{Where Wild Things are} \label{fig:Maurice}}
\ffigbox[\FBwidth]
{\includegraphics[scale = 0.5]{AliceSteadman}}
{\caption{Ralph} \label{fig:Wabbit}}
\end{floatrow}
\end{figure}
\end{document}

subfigure
withminipage
to get1
and2
instead ofa
andb
? – Johannes_B May 26 '15 at 17:23subcaption
package you can get it ... – juanuni May 26 '15 at 17:24