 <p>You should set the new image to the <code>ImageView</code> like this:</p> <pre><code>imagem = (ImageView)findViewById(R.id.imageBody); imagem.setImageResource(R.drawable.my_image); </code></pre> <p>Also note that method <code>rgsexo.getCheckedRadioButtonId()</code> doesn't give you an id from R class, but the id you need to set to the button via <code>setId(int id)</code> method before, i.e. in xml layout file. Maybe it's better to differ your two buttons in group via index as follows:</p> <pre><code>int radioButtonID = radioButtonGroup.getCheckedRadioButtonId(); View radioButton = radioButtonGroup.findViewById(radioButtonID); int idx = radioButtonGroup.indexOfChild(radioButton); </code></pre> <p>So the whole method would be:</p> <pre><code>private String interpretIMC(float imcValue) { imagem = (ImageView)findViewById(R.id.imageBody); rgsexo = (RadioGroup)findViewById(R.id.rgSexo); int selectedId = rgsexo.getCheckedRadioButtonId(); // get the id View radioButton = radioButtonGroup.findViewById(radioButtonID); int idx = radioButtonGroup.indexOfChild(radioButton); switch (idx) // switch on the button selected { case 0: if (imcValue &lt; 20) { imagem.setImageResource(R.drawable.slim); return "Abaixo do Peso"; } else if (imcValue &lt; 24.9) { imagem.setImageResource(R.drawable.normal); return "Peso Normal"; } else if (imcValue &lt; 29.9) { imagem.setImageResource(R.drawable.fat); return "Acima do Peso"; } else if (imcValue &lt; 39.9) { imagem.setImageResource(R.drawable.fat); return "Obesidade Moderada"; } else { imagem.setImageResource(R.drawable.fat); return "Obesidade Mórbida"; } break; case 1: if (imcValue &lt; 19) { return "Abaixo do Peso"; } else if (imcValue &lt; 23.9) { return "Peso Normal"; } else if (imcValue &lt; 28.9) { return "Acima do Peso"; } else if (imcValue &lt; 38.9) { return "Obesidade Moderada"; } else { return "Obesidade Mórbida"; } break; } } </code></pre>